HermitBehFAQs

FAQs about Hermit Crab Behavior

Related Articles: Hermit Crabs, Crabs, Marine Scavengers, Fresh to Brackish Crabs,

Hello crew! Hermit eating Aiptasia 9/12/15
Hello Bob and team!
<Howsit Renee?>
I was just browsing your site reading up on Aiptasia controls and the Q&A postings and thought I could pass along a little experience of mine.
Back when I was less informed and overfeeding my fish (thanks to your forum I've corrected the errors of my ways.... I think?), I had a little colony of Aiptasia sprout in my side-hanging overflow that went unnoticed for a very long time. The colony seemed to be confined to the little box so I just left them undisturbed as to not 'wake the beast'. I've kept a watchful
eye on them and their progress through my sump. I really plan one day to purge them, but for now I let them remain. They're kinda cute all trapped in there. Anywho. I digress.
Every now and then a spore makes its way through the gauntlet of the sump, the fields of macro algae, and finally the return pump into the display tank, taking hold somewhere and making himself known. What's very interesting though is that I was mistakenly given a Dardanus Megistos in an order of small hermit crabs back when I first started my tank. He's been quite the little adventure to keep around! He's about the size of a baseball now, having filled out the largest shell I've been able to acquire, and has taken out a lawnmower blenny and dragon wrasse as unfortunate victims. He even likes to swat at my large Humu Humu if he gets too close. Brave little guy.
What I've noticed is his love for the Aiptasia. He will violently attack and devour them on the regular. His love for them is the only reason I've left them unresolved in my overflow. They're his dietary supplement it seems!
I just wanted to pass on a little first hand experience with these hairy monsters as very useful Aiptasia controls!
<Thanks>
Thanks for hosting such a resourceful site. My tank wouldn't be as successful as it is if it weren't for all your teams' help!
Sincerely,
Renee
Godzilla, in his younger days.
<Cheers! Bob Fenner>

Marine hermit crab acting weird 1/30/15
Hi y'all-
<Ryan>
I think I've got a weird one for you:
Last summer I inadvertently abducted a hermit crab from Pensacola bay. I've kept him alive thus far, much to my amazement, in a tank that is admittedly much too small and lonely, but apparently adequate until I can repatriate him.
Here's the weird part- for the last week or so he has latched on to a fake plant in the tank with a death grip, never letting go. He still eats, but i have to drop food right on him and he still hangs on. Any clues?
<A terrible hankering for greens; plastic or real?>
He has molted once, and got back in the same shell. The shell seems pretty big for him. Not sure where to get a bigger one.
Thanks for any help you can offer.
<Got me; something missing in its diet, its need for... a statocyst? Bob Fenner>

Red Hairy Legged Hermit Crabs, growth, beh. 12/3/12
I just have a simple question that I can not seem to find the answer to: I used to work with hermit crabs, the ones that don't live in the water though, and I was told that they will grow as big as they need to in order to fit the shell they have chosen. Are reef hermit crabs the same?
<Mmm, no>
If I give my red hairy legged hermit crab a very large shell and he decides to try it out will he grow to fit it? Or is there a maximum size that the crabs grow?
<Per species, yes... some are quite small, others.... BIG! And dangerous to livestock. Bob Fenner>

Hermit Mating Dance? 2/24/12
Hello! I noticed the two Blue Legged Hermit Crabs I bought today where <were> attached face to face. At first, I couldn't tell if there where two fighting or if one was getting into a new shell. The more I watched, the more it seemed like one was fighting the other (from reading on here I know that is a good possibility).
<Oh yes... will pull the other from the shell for it>
So I picked them up and had to (very easily) pry them apart. They both looked unharmed and so I just dropped them into opposite sides of the tank. Then the bigger of the two started putting all of his legs to the sand and raised his shell as high as he could manage (like a mating ritual), which made me wonder if they where mating rather than fighting.
<Another possibility>
All I have in the tank are these two hermits plus one red legged hermit and a 2.5 pound live rock as far as life is concerned. I also have 10 various sized shells for them to switch to should they need it. All of that to ask, do you think they were fighting or mating? Thanks.
<Can't tell from what is presented here. Bob Fenner>

Dardanus megistos, beh. 9/27/10
I acquired a Dardanus megistos hermit crab about a month ago and I am keeping it in a twenty gallon aquarium with Fluval canister filtration.
It was doing well and growing quite rapidly. It has changed shells three times already. About three days ago it took up a spot against the rear wall of the tank. It has half buried itself in the sand and just stays there, not coming out to search for food, as it used to do all the time. Is this normal behavior?
<Can be, your crab may not be hungry, may be getting ready to molt. This link will lead you to more information on Hermit Crabs.
http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/hermitcrabs.htm>
I had a Dardanus about ten years ago and cared for it until it died about a year later. It was quite huge when it died. As far as I can remember that crab never did what this one is doing.
Thanks for any info on this situation.

Marine hermit crab burying itself in the sand 9/16/10
Hi!
<Good morrow Lea>
My tank is doing wonderfully thanks to the wet web media crew - I greatly appreciate all your help!
<We're glad to share>
My current question concerns one of my red-legged hermit crabs. For the past week he has been burying himself beside a particular rock - shell and all. The first time I noticed it I thought he was dead so went to remove him and saw his legs retract so left him in the tank, though put him in a different spot and pushed sand around to fill in the depression. The very next day he was back at it. He seems to bury his shell in the substrate (aragonite live sand), leaving the opening facing out so he can extend his legs and antennae. As far as I can tell he doesn't move, though he may at night when the lights are off. He is situated immediately under a spot where one of my live rocks is disintegrating (and seems to be doing a spectacular job of taking care of the unsightly "dust"). I'm thinking he's found a spot where he likes and has dug in to claim it as his own. Any thoughts?
<Mmm, could be protecting its shell from competitors (other Hermits), or be hiding from predators...>
Have you heard of this before?
<Oh yes>
I know land hermit crabs like to bury themselves when molting, but he doesn't appear to be molting (being in his shell and all). but who knows. Maybe you? :) Oh, and for what it's worth, the other red-legged hermit and my blue-legged hermits are all doing fine and roam about constantly.
Thanks again!
Lea
<Thanks for this report. Bob Fenner>

Staghorn Hermit Crabs 3/19/10
Hello,
<Hi Joe>
Do Staghorn hermits outgrow their shells, or do their shells grow with them?
<The Staghorn Hermit Crab lives in a branching shell that does not grow with them and is covered with hydroids and bryozoans. The crab itself is hardy, but the shell that it resides in requires specialized care due to the life
forms present on it. The problem with keeping this crab is that the shell can easily be overturned by other animals that may be present in the aquarium. Once this happens, the crab cannot right itself due to the shape of the shell. Staghorn hermits are best kept in a system with other filter feeding invertebrates, or in a refugium where the hydroids and bryozoans on its shell can be fed properly with types of live or prepared plankton foods.>
Thanks,
<You're welcome. James (Salty Dog)>
Joe

Marine hermie hanging out of shell -- 3/14/10
Hi guys,
<Laurel>
We've had our single marine hermit crab for about 2 Â½ years. He's alone in his saltwater aquarium. Has molts pretty regularly (about 4 times since we've had him) and has grown at least 2-3 inches. He eats well, is active and has seemed content in his environment. For the past few days he's been hanging outside his shell ï¿½
<Not a good behavior>
sometimes just his front claws, other times nearly his whole body. Sometimes he wraps his claws around the pump tubing and kind of hangs there. I reduced his water temp a little bit, but he's still doing this. He has several other empty shells in there, but he's admittedly picky. If I make too sudden a movement he'll zoom inside his shell and he fits all the way inside. Is he sick?
<Maybe>
Is he uncomfortable in his shell and wanting a new one?
<Possibly>
He did move over to a different shell today and he's hanging outside that one too. Any thoughts?
<Need more information re water quality (Ca, Mg, Alk...), foods/feeding... Please read here: http://wetwebmedia.com/hermitdisfaqs.htm
and the linked files above... but this Hermit Crab may "just be getting olde">
Thanks in advance ï¿½ you guys are the best.
Laurel Hoitsma
<Welcome. Bob Fenner>
Re: marine hermie hanging out of shell 3/14/10
Thanks for the quick reply Bob. He eats 3-4 shrimp pellets and one algae wafer per day. Although he hasn't had much appetite the past few days. The salinity is at 1.024. I'll need to take a water sample to our local marine pet store to test for the other levels. Unfortunately, we leave town for a week starting Tuesday, so I'll be crossing my fingers. I thought perhaps he might be getting "olde." We'll see.
Laurel
<We will indeed. BobF>

Hermit crabs changing shells en masse: Hermit Crab Beh 4/30/2009
Dear WWM Crew,
<Hi Guillermo>
Thanks for your amazing site! I am writing you with regard to a curious behavior that I have been noticing in my marine hermit crabs for the past couple of days. I could not find any information on-line and was wondering if you have had a similar experience. Here are the details:
I set up a 40-gallon saltwater tank seven months ago. It is currently stocked with one 4-inch Pink Spotted Watchman Goby (Cryptocentrus leptocephalus), one 3.5-inch Fuzzy Dwarf Lionfish (Dendrochirus
brachypterus), two small mushrooms, and 4-5 small Taro Tree Corals (Capnella sp.). I stocked the tank gradually, so most have been with me for between 3 and 5 months. I change 10% of water every week. I tested for water parameters this morning and they seem to be ok (ammonia, nitrate and nitrite are 0, pH is 8.4 and SG is 1.025).
<Sounds good, but your lion will require a larger home down the road.>
I added 4 Dwarf Red Tip Hermit Crabs (Clibanarius sp.) about 4 months ago plus 15 empty shells so that they could upgrade their homes. Each of them has changed shells once since then, one crab at a time. I added one Orangeclaw Hermit Crab (Calcinus tibicen) two months ago, and two Blue-Legged Hermit Crabs (Clibanarius tricolor) and two Staghorn Hermit Crabs (Manucomplanus varians) last Saturday. There are now nine hermit crabs in total. They have not displayed any aggression among them so far.
<OK>
The situation for which I am writing started happening the next day (Sunday). The crabs had scattered the shells over the last months, and I decided to pile all the shells up to create more open space in the tank.
The following morning (Monday), I noticed that three crabs had changed shells (one Dwarf Red Tip, one Orangeclaw, and one Blue-Legged). A few hours later, another three had joined them (one Dwarf Red Tip, one Blue-Legged, and one Staghorn that moved to a regular shell in front of my eyes!). By the end of the day six out of the nine crabs had changed shells.
<Heheh, my hermits did this too.>
My question is whether this behavior is normal, or whether it could be a sign of something going wrong in the tank.
<Not a sign of a problem>
I have heard that a hermit crab vacating one shell may generate a chain reaction where a smaller hermit crab moves to that shell, then another hermit crab moves to the shell of the latter, and so forth.
<Yes>
However, I think this may not be the case here because the shells in my tank have specific shapes based on which I am pretty sure that all of the hermit crabs moved to empty shells that I had previously added to the
tank.
<No, it is what it is, they are just swapping shells.>
Finally, I noticed today that the Staghorn Hermit Crab that had moved to a regular shell moved back to its branching shell, used it for a couple of hours and then moved back to its regular shell. Is this a normal behavior in this species?
<He\She\It is trying to find a shell it likes - Bigger than the one it has, but not so big to entice the larger crabs to try and take it.>
Many thanks for your help!
<No worries here, just enjoy the show.>
Best regards,
<My Pleasure>
Guillermo
<Mike>

Relationship between hermit and spaghetti worm 4/29/09
Hello all!
Is it common or well-known for a spaghetti worm to "host" or form some kind of symbiotic relationship with a hermit crab? I have a Mexican red-leg hermit using a Cerith snail shell with a small hole bored in it (I assume made by the predator which killed the original snail). There are two long tentacles coming out of the hole that to me look identical to a spaghetti worm. They wriggle about and withdraw just as you'd expect them to. Have you seen this before?
Thanks,
Emily
<Hello Emily. It's actually pretty common for Hermit crabs to form symbioses of various types with a number of different animals. One of the European species, Pagurus bernhardus, has been quite well studied in this regard. It routinely forms a symbiosis with sea anemones (several species) that it actually moves from old shells to new shells as it grows. Inside the shell there is a Polychaete worm, Nereis fucata. The crab and the anemone are assumed to benefit one another, the anemone by being moved about and perhaps collecting food from the crab, and the crab gets the benefit of the anemone's sting. As for the worm, there's no particular benefit to the crab, but the worm certainly snatches crumbs of food and lives somewhere relatively secure, defended by both the crab and the anemone. As for worms living inside burrows through the shell, the hermit crab likely doesn't notice or care about these, any more than you do the thousands of mites living in your eyebrows. There's little to no interaction between the two of them, though perhaps the burrowing worms might benefit from crumbs of food that drift about when the hermit crab feeds. Those worms would be in that shell regardless of whether the shell was occupied by a snail, a hermit crab, or was just sitting about on the substrate. As such, it's not really a symbiosis _per se_. It's better to think of a symbiosis as a situation where animals make particular efforts to interact with one another, and when doing so, at least one partner benefits. Cheers, Neale.>
Re: Relationship between hermit and spaghetti worm
Thanks for the info, Neale!! I think it's kinda funny, this crab is hauling around a freeloader! Pretty neat :)
<Some 10% of your (dry) body weight is bacteria. On top of that, there are mites in your eyebrows, amoebas crawling around inside your mouth, yeasts on your skin, and more besides! The only thing unusual about the "freeloader" you're seeing on your Hermit is that it's visible; most aren't. Cheers, Neale.>

Caring for Aquatic Hermit Crab 4/29/08 I don't mean to bother you but I haven't heard back from the email last week and I have looked on the website but can't find a response there so I thought maybe you didn't get the email the first time around. I am trying to send it through again in hopes that you can help me with poor Sebastian's color. <Thanks for re-sending. I don't recall seeing this> When I started this new job March of last year, I thought it was really cool that they had this 125 gal salt water tank. They had a hermit crab that I named (of course) Sebastian. He was very active pretty much at all times. It wasn't long before our "fish guy" informed me that he would have to go; he was getting too big and aggressive for the tank. <Is an aggressive, predatory species...> He was evicted for not playing nice with the residents. He was eating the smaller fish. The person that maintained the tank prior to me arriving should never have put this type of crab in the reef tank. <Actually... a false crab, Anomuran...> What did I know, I was just fascinated by him so I asked if we could get a smaller tank to keep him in. That was last June, we have put him in my office so I get to keep a close eye on him and I have learned alot. <... no such word> I learned that they molt and bury it. He has grown a great deal and we have replaced his tank for a bigger one , 25 gal.. I have also noticed that he used to be a darker orange color where he is now a very light almost yellow color. Every time he molts, he gets paler in color. He is not as active as he used to be. I have tried to find out information on him but there just is not alot out there on the care of "Aquatic" Hermits. <Actually...> My fish guy doesn't know much on them as well. He just cleans the tank, he doesn't much care. He gets fed frozen squid and frozen silver fish. <This is the source of "trouble", color-loss... No Carotenoids et al. > I have attached a few pictures, the first one was before Christmas when he was dark orange and then the other was just a month or so ago; you can see the difference in color. He has molted again since the last one. He is on about a 3 month schedule. It takes him about a week of hibernating, then 3-4 days to harden then he is ready to eat again. Is there any information you can give me or any websites you can direct me to. We have a handful more in the bigger tank but they are all pretty small, the biggest is the size of a quarter - down to a dime. I have been told that they are the red legged Hermits. They don't seem to grow much. If you could also let me know what kind Sebastian is that might help. Kathy - FSI, Financial Solutions - Hermit Crab Lover <Needs more/better nutrition... with pre-cursors that will supply the color elements. Please read here: http://wetwebmedia.com/hermitfdgfaqs.htm and the linked files above. Bob Fenner>

Re: Caring for Aquatic Hermit Crab 5/7/08 Hello again, <Kathy> I just wanted to thank you for you great advise. We have added a great variety to his diet and his color is already improving. He has also gotten a lot more active like he used to be. My not so little guy never stops. He has even changed into a much larger shell - he thinks he is bigger than he is. I just love to watch him. Again, thank you for your help. I have pasted it on to my fish maintenance person so that he also can learn from it. <Ah, thank you for this upbeat update. Bob Fenner>

Hermit found a new home Mobile Mushroom Coral (Coral Attached to and Occupied Snail Shell!) 3/30/08 Hey Guys, <Scott F. your guy tonight!> I have a potential problem with a hermit crab and a Mushroom Coral. A few weeks ago, I bought a frag of Mushroom Coral that happened to attached to an abandoned snail shell. Unfortunately, a hermit crab in my tank has decided to make a nice home out of it. <Too funny!> How do I go about getting the frag off that shell?? I'm worried he's going to move around and kill the coral. I've included a picture of this for you all to laugh at. Thanks! Chris <Actually, Chris- I'm not laughing! I'm kind of stoked for you! I've put this idea out there in some of my talks on aquascaping that I give at clubs- A living, moving bottom "substrate", comprised of Ricordea or Mushroom Corals attached to snails! Think about it- If you have 20 or so specimens attached to snail shells, you could have an ever-changing, super colorful coral display! Ok, in all seriousness, if this doesn't appeal to you, I'd simply provide a few larger empty shells for the hermit to colonize as he/she grows. It's inevitable that the animal will abandon it's current shell for a larger home when the time arrives. If you are VERY careful, you could use a razor blade to remove the Mushroom, but I would advise against it for fear of injuring yourself and two animals. In the meantime, I'd enjoy the antics of your "Mobile Mushroom". You can make a sort of game of it, taking bets from friends as to were it might show up! Good luck, and enjoy the show (for now). Regards, Scott F.>

Dardanus megistos Lifespan - 3/5/08 <Hi Andrew> Any idea what the lifespan is for Dardanus megistos? <Hmmm, good question. I can't find an exact number for this species, but my guess would be somewhere in the range of 2-4 years depending on whether it's a male or female. It seems that male hermits usually live a bit longer than females. The range I've seen for hermits in general (in the wild), has been anywhere from around 18 months to 10 years for marine hermits and up to 30 for land hermits.> Thanks Andrew <You're very welcome. I'm sorry I couldn't give you an exact answer! -Lynn>

Re: Dardanus megistos Lifespan - 3/5/08 Lynn, <Hi Andrew.> Thanks for the response. <You're most welcome.> I have had mine since early 2003 so it is already 5yrs old. <Neat, especially considering that we don't know how old it was when you got it!> I don't know if it's male or female. <That's understandable. These hermits don't have any distinguishable differences (externally) between male and female.> Andrew <Thanks for sharing. Take care, -Lynn>

Legless Crab... or not? 7/22/07 I have three hermit crabs who live in the same tank together. <OK.> I went to check on them earlier and saw several, <Saw several what? I presume by the title you mean legs here...> including the claw, lying in the sand next to one of the crabs. I didn't actually see that this crab's legs were missing (he's shy and rarely is seen by anyone), but I checked my other crabs and they're doing fine. I isolated the nearly legless crab in a tank by himself, assuming he had no chance to survive, but when I checked on him later, I saw he wasn't missing legs at all! <OK.... so the legless crab isn't legless after all? Fuzzy wuzzy wasn't fuzzy was he?> However, he is looking smaller and pinker than he was before. <Sounds like he molted.> I know it wasn't molting, because they were real, whole legs. <Molting still may be a possibility.> what is going on with my crab?

Re: legless crab - 7/23/07 first of all, when crabs molt, they shed their exoskeleton. these were, as i said, WHOLE legs, not exoskeleton. second, i can count. <Your written word doesn't so much convince me.> i know how many crabs i have. <Ever hear of hitchhikers?> third, why do you and your god damn crabs care if i use "i" instead of "I"? is it really that offensive to you? <Because its proper English, and I have to correct it. Fix and resend. Read more reasons why here: http://www.wetwebmedia.com/QueryCorrsRefPg.htm Mich><<Mmm, could be ecdysis... RMF>>

I couldn't help myself! 7/25/07Crew, <Mike> I can't believe the grief you receive trying to help people with problems/questions who come to you! I had to comment on a couple of items in the daily FAQs. In regard to the individual upset about the search feature, a quick way to find what you want in a page full of threads is to do the Google search, open one of the links suggested, then in the pull-down menu of your web browser click edit, then find. Type in what word/phrase you are looking for and click "find next". Continue clicking "find next" until you are at exactly what you went to the page for. For the individual who "knows how many crabs s/he has", I "knew" I had no Mithrax crabs in my tank until I found one hiding in the rock. Hitchhiker indeed! Mike <Thank you for this input and commiseration. Bob Fenner>

Lost Hermit Found 7/17/07 Hello Crew! <Hello> You guys/girls have been such a help I figured I owed you at least a good pic. I couldn't find my hermit for a day. All 3 shells were empty so I took him for dead. But the out of the back rock here he is in his new snail shell. My wife nearly died when she saw him. So here he is! Thanks again. Notice the nice DSB you wonderful people told me to do. Ammonia 0 Nitrite 0 Nitrate 0?was 20-50 till the bed kicked in.) <Thank you for the kind words, and thanks for sharing your pic. James (Salty Dog)>

Re: Question about red legged hermit crab activity. - 06/28/07 Thank you very much for the quick reply! <Welcome> However, this being my first tank, I think I'm probably just being TOO cautious. <Possible... but good!> All of the crabs are moving fine, I never see them sit in a spot for more then 2-3 hours. But they do seem to be more active at night.. They are scarlet reef hermits. <Ahh! Paguristes cadenati. These can take a while to adapt, be more active during light-hours...> Thank you once again! <Welcome! Bob Fenner>

Hermit beh. 5/8/06 I recently purchased two hermit crabs. I have attached a link so you can see a picture of the type of species that I believe them to be. When you get to this link there is a band of four pictures at the top and then one picture of a red/orange crab below that. That single picture is what I believe to be the same species as my crabs. My only question is, I just recently had one molt but he has not gone into a bigger shell yet. I am just wondering, how often do they molt, and how often do they need to move into a larger shell? <Mmm, can be every few weeks depending on conditions favoring growth... food availability... sufficient alkalinity, biomineral content... and new/larger shell homes at about the same rate> Any help you could give on this would be greatly appreciated. http://www.seafocus.com/species_crabs.html<http://www.seafocus.com/species_crabs.html> Also, I love your website! Katharine <Thank you. Bob Fenner>

Lazy Scarlet and Blue-legged Hermit Crabs 11/5/06 Hello crew at WWM <JM> just a quick question I have blue and scarlet hermits that lay around all day (for days) and are still in the same place the next morning --- <Trouble... something likely amiss with your "water quality" here... possibly endogenous poisoning...> no they are not dead (smile)-- however they are not actively feeding on the algae, in which I purchased them for. <Most species of Hermits are not so inclined to do so... if there are other types of foodstuffs available> I also have zebra-legged which are constantly feeding. I won't go into the parameters in my tank except to say that corals, fish and other inverts are thriving alive with voracious appetites) Nitrates are less than 20 ppm. Generally I do not use supplements except I do use Kalkwasser and a few (5) of drops of iodine (Kent marine) twice a week in a 75 gallon tank. I do feed the tank for the Brittle stars, maroon clownfish and the blue-lined surgeonfish (Acanthurus nigroris. The question is if I am feeding the tank are the hermits losing interest in the algae because they are scavenging? <Yes... you are likely correct here> and is there anyway to encourage them to eat algae short of placing them on the live rock with the algae? <Heee! Making other foods scarce> and lastly I understand they are generally hardy is there a particular tank parameter that needs to be checked that would have a negative impact on the crabs?? <Mmm... are actually "false crabs", anomurans... Need biomineral, alkalinity as per your cnidarians... other essential macro and micro-nutrients can/should be supplied via feeding...> Thanks in advance for your response <Welcome. Bob Fenner>

Re: Singing, backward moving Crustaceans along the Euphrates? 8/14/06 Thank you very much for taking the time to answer. <Welcome... I have a classics minor from my first degree... a persistent interest in antiquities matters> Hermits chirp. Though I've never heard them there are recordings on line and mention of it on some sites. <Must stridulate at low amplitude and intensity> I thought the problem was with freshwater since the text says "river crabs" alongside frogs implying fresh water. I didn't think there were freshwater hermits. Is there anything else that looks like a crab and might make some kind of noise along a river or canal? <Mmm, not a crustacean as far as I'm aware, though there are some freshwater hermits. I suspect that this reference may be to an insect of some sort... perhaps a cicada or cricket species. Bob Fenner>

Marine Hermit Crab Die Off and Stocking Density (Give, Your Crabs a Shell) 11/28/05 Hello Crew, <Hello Tom.> I really appreciate all the help you've given me over the last couple years...thanks! <Glad you have found us useful!> Today I'm hoping to get an informed opinion about what might be happening to my hermit crabs. <Okay.> My tank is a 30 gallon with a two-inch Fire Shrimp (Lysmata debelius), a Yellow Clown Goby, and a Firefish. It also has a small crab (size of a dime) and probably a very small brittle star (all I ever see is his arms sticking out of a hole in the rock a quarter inch or so). These latter two hitchhiked in on the live rock. <Good stocking choice so far, but watch out for the hitchhiker crab or at least try to i.d. it, could turn out to be something large/predatory in the future.> The tank has a larger grouping of rock on the left, and a smaller grouping on the right, with a few inches separation in the middle. The Fire Shrimp lives in the left rock grouping, basically all alone. Everything else lives in or on the right rock grouping. I only mention this because it seems so odd that it might be a clue. About two months ago, I ordered a dozen Dwarf Red Tip (Clibanarius sp.) and a dozen Zebra (Calcinus laevimanus) hermit crabs to control algae. I received generous counts, and actually started with about 30 hermits. As of today, I can count only 11 hermits. There may be a few I can't see, but 19? <Honestly Tom I think the reason for this hermit die off is the original stocking density. These animals simply aren't built to live a crowded arrangement like this but they are plagued by retailers recommendations of 1 per gallon, which is quite irresponsible (not you them). Anyway there are probably a few contributing factors including fighting over shells and insufficient food. Unless you were target feeding the hermits its unlikely they were able to survive simply as detritivores or scavengers. A more appropriate stocking level is 10 or less.> I also believe a hitchhiker snail has disappeared. <Possibly killed for its shell.> So, what do you think is happening to the hermit crabs? <See above.> Tom <Adam J.>

Hermit Crab Interaction 9/25/05 <Adam J.> About 6 weeks ago I purchased a red legged hermit crab to help keep my 3 month old saltwater tank clean (and because the kids loved it) but yesterday the crab was directly in front of the tank while it was eating. I sat and watched it for a minute and all of a sodden I saw a little crab come to the very front of the shell and the elder then kind of pushed it back with one of its legs, like it was protecting it, it looked to be maybe a ? an inch in size maybe a tad bigger, with well developed pinchers and all, it hung around for a minute or so then poof it run back into the shell were I couldn't see it, though I did see it for a minute today as well. I'm assuming that the little crab came along with the other when I bought it. <Possibly but its more than likely a live rock hitchhiker. Are you sure it was another hermit or did it look more like a flat "true crab" that was just pestering your resident hermit? It is extremely unlikely that this is a parent/offspring relationship. In general crustaceans do not provide post-birth for the young, eggs are released into the water column where young hermits live a pelagic/plankton life until they can grow and find there own shell, they then fend for themselves.> The big crab also molted within the last 2 weeks and is in a shell about 3 inches long, it was pretty dormant for about a week. <Normal for most crustaceans to hide post-molting.> Is it common, do they often carry babies in their shells? <Not in my experience.> What should I do to get the baby into its own shell? <If it is a hermit it will eagerly go into any shell provided of appropriate size.> What size shell should I get? > your description, a very small one.> Thanks, Richard <Make sure to read through the WWM FAQ's for more detail on hermits and their behaviors, Adam J.> Re: Hermit Crab Interaction 9/25/05 I got a good look at what was inside today, I think that it looked like a little shrimp, could it be that the hermit just can't get it to leave or get to it in the shell? I think it may be one of those feeder shrimps, how big will that get before it comes out? <Without a picture it is nearly impossible to tell what species of shrimp this is, there are a few types of shrimp sold as "feeder shrimp." My guess would be a common live rock hitchhiker such as a Mysis shrimp, a copepod or amphipod.> Thanks <Anytime, Adam J.>

Hermit crab behavior 8/26/05 I have 4 red legged hermit crabs and I keep noticing one crab filling the other crab's shell with sand. What is the crab doing? Is this normal or is it trying to kill the other crab? Thanks, Michelle <Bizarre... maybe trying to get the other crab out of the shell so it can occupy it. Bob Fenner>

Hermit out of his shell 07.04.05 One of my hermits is out of the shell and crawling around the tank unprotected, what can I do???? <Keep the humidity up, offer him a variety of shells with different size openings, and if possible put other crabs in a different enclosure until this guy figures out what he is trying to do, they are very vulnerable when out of their shell. Oh, also provide some damp sand a few inches deep, he may be feeling the need to molt, and will need to bury himself. Gage>

- Staghorn Hermit Crab - Hi, We've had a Staghorn hermit crab for some time now and have noticed that over time his shell has gotten dark and shriveled-like. I'm assuming that it is dead or dying. Tonight, we have noticed that the crab has abandoned his shell and has moved into one of our spare regular hermit crab shells. But has not managed to flip the shell upright yet (too big perhaps?) <Perhaps give him some help.> Will he live in a regular shell? <I would like to hope so... as neat as Staghorn hermits are, they rarely get to live for long in captivity because their shelter just doesn't make the transition. Perhaps this one will have a better chance because it's moved on.> My husband has put a few smaller shells around him. Is there anything else we can do for him? <Flip him right side up.> Other info about tank: 55 gallon tank 260 watt light tank mates: coral beauty angel bicolor angel clownfish several damsels snails cleaner shrimp 2 electric blue leg hermits 1 red hermit Any advice is greatly appreciated. Thanks! Kimberly <Keep an eye on him, and make sure he gets upright. Cheers, J -- >
- Staghorn Hermit Crab, Follow-up - 30 Jun 2005 Thanks for getting back to me so quickly and for providing me with all your input. <My pleasure.> By the next morning, he was upright and doing his thing (sifting sand) as always, just like he did when he was in his original shell. Now, several days later, he seems to be doing fine. <Excellent - glad to hear.> Thanks again! Kimberly <Cheers, J -- >

The Gathering - Hermits Good evening! <And to you> I haven't written in a long time. When I did, you and your teammates were a great help. My tank is up and running great. 150 gallon SW reef tank. Up for 10 months. Almost fully stocked. Never had any problems. Thanks to your site. This isn't really a question, more of an observation. So the last couple of evenings when the lights go out I notice my hermits acting kinda strange. (At least I think it's strange). When I shine a flashlight in the tank, all the left handed hermits are gathered on the same rock huddling together. (About 12 hermits) On another rock, all the electric blue hermits are huddling together as well (6 hermits). Finally on another rock, all the scarlet red hermits are gathered as well. (4 hermits) This is new to my tank. Almost every night I will observe the tank with a flashlight. Night observation is almost better than during the day. I'm fascinated with all the life at night. The gathering of the hermits has only been going on for three nights. Have you or your mates heard of this type of activity? Common? Strange? <Mmm, "hermits of a feather/species do flock together"... particularly during spawning times... you might log your observations, look for positive correlation with moon phase/tides> So much for not asking a question... Oh, also last night I noticed one of the left handed hermits releasing eggs into the water. (At least that's what I think it was). A left handed hermit kinda lifted the shell off her/his back and hundreds of little (little) eggs/things were released into the water from her back. They looked similar to live brine shrimp. Does this sound like common hermit activities? <Mmm, yes> Were they releasing eggs/hermits? <Likely so> I though this was pretty interesting, so please let me know what you think. Thanks for your time and great site. I still read it daily. Dan <Me too! Bob Fenner>

My hermit crab has left his room My hermit crab left his shell, what should I do? <He's probably gotten too large for the shell to be comfortable, I would toss some more hermits in there or some empty shells and he'll find one that fits. Good Luck! LinearChaos.>

Hermits fading Dear WWM Crew, Thank you for the great site! I have browsed through your website but did not find the answer to my problem. I have 10 blue legged and 2 scarlet hermit crabs in 55 gallon tank. I have recently noticed that my scarlet became more of an orange color and at least one blue legged has faded in color too. Can you suggest any reasons for that so that I could address it before they get worse. Thank you! Artem <Likely nutritional, though water chemistry/quality can definitely play a/the role here. Color change per se is not an indication of good or ill-health though... You might check your water, augment, actually directly feed your Hermits some vitamin/supplement (e.g. Zoe, Selcon) soaked foods. Bob Fenner>

Hermit crab mating dance? Hello WWM Crew, <Kari> I watched something strange with my hermit crabs this evening and I was wondering if it was mating, or just simply checking out each other's shells. If you have any clue - please share! <Okay> I bought 5 Clibanarius hermit crabs from my LFS (only one is the C. tricolor with the blue legs, the others have reddish legs). I noticed one of them was getting "attacked" by all of the other 4 at the same time. I separated them and then they all ran back and "attacked" the same one all over again. I decided there was nothing I could do, so I'd just watch and see how it played out. Three of the smaller "attackers" eventually lost interest, leaving a large blue-legged "attacker" in a tan shell (blue), and a red-legged "victim" in a white shell (red). This is what happened: 1. The blue one turned the red's shell over, put his front legs into the white shell, and kept knocking his tan shell on the red's white shell. 2. The blue one came out and pulled the red one out of his white shell. The red one crawled out and sat on top of the blue's tan shell. 3. The blue one came completely out of his tan shell and went into the white shell. 4. The blue one sat happy in the white shell for a little while 5. They rolled around for a bit 6. The blue one came out of the white shell and went back into his original tan shell. 7. The red one went back into his original white shell and everyone was happy. They just walked away from each other. The corresponding pictures are attached. Is this just the blue one checking out the red's shell and deciding he didn't want it after all? Or was this some sort of mating? <Not mating... different species... perhaps a test for the red one's shell...> If the red one in the white shell was "in heat" (for lack of better term) then that would explain why all the others kept attacking it... Anyway, it sure was interesting and I'm curious to know what was going on. Thanks! Kari <Me too... these false crabs (anomurans) are almost constantly contesting each other for food, space, shells... Do provide a few extra shells of various sizes for them to sort amongst. Bob Fenner>

Hermit Crab Fighting or Mating Hello, <Hi Leah, MacL here> I have had 6 hermit crabs 2 very small, 2 small, and 2 medium for a little over a month now. They always romp around and play. Today I noticed that the 2 very small hermits were attached to each other...like one had one of its legs or claw inside the others shell. <Very likely trying to pull the other one out. When I see this I usually separate them and move them to opposite sides of the tank.> I thought it strange so I separated the two to opposite side of the tracks. Just to see the one crab climb back and reconnect with the other. I figured they were playing so I left. When I re-entered the room 5 minutes later one of them was completely out of its shell and the other was hovering over top of it. I immediately jumped to the conclusions that the other crab was trying to kill the one out of its shell. I picked up the shelled crab and moved him away and put the a shell next to the other crab...it gladly climbed in and has been hiding all day. The other crab has been stalking it and just staring at it from a distance because it can't get back to where it is hiding. Is one of these crabs trying to kill the other? <Not necessarily kill but definitely after the shell.> (we have plenty of other shells that it could choose from!!) <Sometimes they want what they want> Or is it just a determined mater.....PLEASE LET ME KNOW! I keep checking on them to make sure they're ok! Thank You, Leah

Stuck on You I have two hermit crabs and they are stuck together. All you can see are the two shells, you can't see the crabs at all. They have been this way for at least 12 hours. Are they dead? <Ryan with you. No way to tell for certain, but wait it out. Just leave them alone, as your other hermits will be happy to snatch up an empty shell. See ya, Ryan> Thank you, Lorraine

Magic Crabs! The Endless Crab-fest-o-RAMA! >This might sound like a preposterous event/question, but I swear it's all true. >>NO! Really?? Let's hear it. >Two weeks ago I bought 6 red-tip hermit crabs for my 55 gal saltwater tank to see if they would get along with my other tank inhabitants (2 percula clowns, yellow tale blue damsel, bubble tip anemone, and a red brittle starfish) before I bought more. >>More hermits? If so, you would probably be doing them a favor if you kept their numbers around oh.. maybe one/10gallons. >Since then two have died, I scooped their little bodies out of the tanks (they died out of the shell, probably because another crab killed them and took their shell) and threw them. >>You just threw them, tossed 'em like a cat? In the house? Where'd they land? Does it smell now? (Sorry, I cannot resist.) When you say "out of the shell", I assume you mean their flat, the shell they use for a home, not the shell that covers their little exoskeletal bodies, correct? >Now today, I have noticed that I still have 6 crabs, I counted them ten times to make sure I wasn't counting anyone twice. >>Heh.. good thing you didn't end up with 60! >Now for the question: >>Indeed! >How is this possible? >>They molted and you tossed the molted exoskeletons. All creatures that are bound by an exoskeleton must molt to grow/make repairs, as they haven't got skin like us endoskeletal beings. >Can the crabs produce offspring this big this quickly? >>Nope, they can't, plus I bet you didn't have any extra flats even if they could. >If you could comment on any of this I would greatly appreciate it. >>Ohh.. I think I'll stop right here. A LOT of folks get really confoozled when hermit crabs do this molting thing. They're quite good at it, and it looks and feels for all the world like their dead, lifeless bodies. >Thanks, Jessica Ressler >>You're welcome Jessica, and no, you're not going crazy. Marina

Blue legged hermit aggression - 1/27/04 Hi crew, some 6 months ago I bought a couple of tiny blue legged hermit crabs from my LFS, they warned me at the time they may have trouble with the existing 5 red legged hermits, <Sometimes known to become aggressive for shells> anyway they have continued to grow well and are now much bigger than the red legged hermits but I am concerned they are now feasting on my livestock! <OK> 2 days ago I notice my blue starfish who has lived happily for the last 9 months has some chunks out of one his legs, <Check water chemistry. Starfish are indicators of water chemistry issues (high salinity, temp swings, or general poor water quality) Also depends on the type of hermits but likely not a dwarf blue hermit's doing> some weeks ago I also caught one eating a snail. <this they are known to do. When they like a home they just move in regardless of inhabitants. Kind of like a house and the fridge is stocked with food> today I discovered the two hermits were eating my cleaner wrasse who I put in the tank 2 weeks ago, the wrasse seemed fine last night. <Likely the wrasse died and they are feasting on the result of the death. Again, depends on the hermits we are talking about. I would try to ID them just to make sure> do you think these are scavengers or predators? <More than likely scavengers> should I feed them or remove them? <You should always supplement them with food. Keep an eye on them. Check your water, and ID them to be sure you don't have a more aggressive predatory type crab. Good luck. ~Paul> Ron

Scarlet reef hermit Bob, I have been using the website to help me with a lot of questions, its great! My question is, Do Scarlet reef hermit crabs molt their hard bodies, I know they switch shells when they grow out of their current ones, however this morning when I looked into the tank I saw what looked to be the body of one without the shell laying on the Live rock is this common and nothing to be alarmed about or do I need to go on a mission to find the killer? <All crustaceans, including the Hermits undergo ecdysis (molting) to allow for (generally positive) growth... and often leave their old exoskeletons about (better to leave in the tank as the old owner may ingest/incorporate the matter into its new one... and it won't pollute your system).> Thanks as always, Mike <The next few days after molting are dangerous for the "soft bodied Hermit"... don't disturb the landscape if you can avoid it. Bob Fenner>

Re: scarlet reef hermit Bob, Thanks for the ultra fast reply!!!!! One last Question what does the molted exoskeleton look like? <Initially, like an exact model of the original... sans the insides... eventually, just bits and pieces...> I'll try to describe it the best I can. The legs are red, and look exactly like the legs on a living crab, same red color/length, the abdomen looks pale white, almost a milky color and seems to wave in the current freely, it appears it has those small legs use to move in and out of the shell, however its not too large in size, but then either was the hermit to start, and its laying upside down. I don't know how greatly this will help but I'm so concerned for in the case its dead, ill need to make sure its not something in the tank killing them. <Might be a molt... with some of the mineral and matrix content going... Not to worry. Bob Fenner> thanks, mike

My hermits are becoming reclusive! 07/23/03 <Hi Chris, PF here with you tonight> I picked up 9 "zebra hermits" (although I swear they're blue-legged hermits by visual identification) at the LFS for some hair algae control, as well as 4 Astrea snails. For the first few days, the hermits chewed away happily at the algae, and tended to congregate in small meetings. It's been a week, and all the hermits have seemed to crawl into crevices in the LR. They all have their antennae (?) wiggling about on their faces, but they remain in there at leisure. Are these creatures nocturnal? I'm somehow doubting that. I know any aquarium won't live up to what my ideal 'bustling with life' scene might look like, but I was hoping for a little more action out of these guys. Should I be looking towards water quality issues? Everyone deciding to molt simultaneously? The Astreas seem to be faring well, happily chewing away at the algae. 3 seem to be doing fine. The last one is quite lethargic, moving at a snail's pace, as it were.. I will be doing ammonia/nitrate tests in a few minutes. pH is hovering at 8.2; s.g. at 1.024; temp ~82F. P.S. Since I last wrote to WWM a couple of months ago, my so-called "hard cure" has long since become quite rewarding, and I could not imagine ever wanting to buy "fully cured" LR! Tons of creatures lurk in the depths of my tank, including strange translucent tentacles (approx 1mm in diameter) that shoot out of tiny holes in the LR and suck in detritus with their vacuum-cleaner like tips (any ideas on what that might be btw)? Thank you for providing this wonderful service WWM crew! Enjoying this hobby, even if I am making all the beginner mistakes one at a time, - Chris <Well Chris, they could be blue legs in zebra snail shells. A rose by any other name... As for their behavior, remember, they don't read the same books we do. I've certainly seen my animals doing things that they're not supposed. The critters on the rocks, are probably some sort of worm, maybe the spaghetti worm, check here for more: http:// www.wetwebmedia.com/polychaetes.htm Mistakes, well, I try not to make beginner mistakes myself, but all new ones. ; ) At least it was one at a time, and not all at once. Have a nice night, PF>

Hermit crabs in Fiji The other night, here in Fiji, there were about 2,000 hermit crabs all trooping up from the beach into the woods at the back of the house. I'd really like to know why they were doing this. <Me too... there are "crab aggregations" timed to tides, moonlight... that involve reproduction en masse. Maybe this is one of those? Optimizing chances collectively, decreasing likelihood of annihilation by predation... Bob Fenner>
Re: hermit crabs in Fiji Thanks for your thoughts. I see that land hermit crabs have to go to the sea to spawn. Maybe these were coming back. Or do they spawn and die? <As far as I'm aware, all spawn and return to land for consecutive years. Bob Fenner>

Hermit Homes, Aiptasia Mr. Fenner First Off I would like to say I really like your book I have found it useful in so many situations. <Ah, deeply gratifying to hear/read. Thank you> I have several questions. One Is: In your book you say that Nudibranchs are not suited for home aquariums because not much is known about there feeding. But recently I have been seeing many ads for lettuce Nudibranchs. They say they take care of hair algae. Do These really work or is it just a gimmick. <They can work. Not so specific in foods (algae) that are taken...> Another do blue leg hermits and scarlet hermits outgrow their shells. <Yes> If so how often do they need new ones and how much bigger should they be. <Provide several of varying sizes and let them choose> What happens if they don't get them. <Not a pretty story. Get larger, no where to move, get eaten by their fellows, other species> Lastly in my reef tank there is this "thing" attached to my live rock. it's hidden by a small pile of rock about a cm. high) and it has several hair-like, very thin, tentacles about 3-5in.) that reach out into my tank's gravel and pulls up stuff from the gravel. Do u know what this is? <Sounds like a Glass Anemone/Aiptasia... read about them on the WWM site> Does it sting? <Yes> It seems to put out a lot of waste it excretes it all at once and it seems to be a lot for how small it is <Bob Fenner>

Hermit crabs Hi Mr. Fenner. I have another question once again. Do hermit crabs also molt, or not since they keep looking for bigger shells? <They do indeed molt> I ask this because if they don't molt, then I have something going on in my aquarium that might sound strange. I have six red legged hermits, and two that are very dark, almost black. I've had them for months, and every so often I find what looks like the remains of one of them. I say remains because it looks like they have been eaten, and all that is left is the front part, like the head, and legs. sometimes the remains are red, and other times they are dark, which shows that both types that I have are doing this. It's not a clear shell like when my different types of shrimp molt, but actually looks like the remains of the body. Yet when I take a roll call, all of my hermit crabs are still alive, and well. <Good observations, relating... No worries... keep supplying a selection of "new homes/shells" to move in to. Bob Fenner> Thanks Greg.

A curiosity (Hermit Crab behavior, speculations) I don't have an aquarium or keep hermit crabs but I'm familiar with these little guys because I grew up on the Texas Gulf Coast... Rockport, TX to be exact. Many years ago a friend and I spent most of the summer at the beach. As always, we saw several hermit crabs doing what hermit crabs usually do in the surf. However, one day (I can't recall if it was late June or early July) we noticed what had to be Thousands of hermit crabs congregated in one area of the beach that was sheltered by a concrete wall and large concrete slabs so the surf was very calm. They were everywhere; some were stacked up on each other five or more crabs high. Others were just crawling about in the shallow water, frantic. But so many! Being curious, we started watching what they were all about. Well, it was amazing. I have never seen such shopping for outerwear! The hermit crabs in the shallows were trying on each other's shells. Some willingly and others not so willing. They were trying on the occasional empty shell found on the bottom or a likely piece of trash or junk floating about. Some were crawling around shell-less, having lost their shell to a rival we supposed. At this point, we made a quick trip to the closest sea shell shop and bought several 'homes' for the homeless hermits. We 'sold' all the new 'homes' and could have used more. We also experimented with the hermit crabs that were stacked up on the concrete slabs and when put in the water they were just as eager to explore a change of residence as the others. By this time it was late and we had to go to Our homes but we made plans to come back to the same spot the next morning. The next day when we arrived the hermits were gone, for the most part. And the ones that remained were not in the least interested in trying on the new shells we had brought with us that morning. Do you have any idea what was going on with these guys? <Home shopping spree? Mmm, does seem (albeit teleologically) that there is some species survival value to such "let's change out at the same time" shell-swapping behavior... as opposed to not switching at about the same time, place... in the way of avoiding predation... and maybe some greater degree of reproductive behavior going on all the while...> It didn't seem to have anything to do with outgrowing their shells and we didn't detect any 'romantic' goings on. I would really like to know if anyone else has seen this type of behavior. Thanks. Jacki <Have noticed Hermit aggregations at times/places... and thought maybe they were coincident with food availability or tidal action... Don't know... but perhaps others will chime in with the posting of your note on the Daily FAQs: http://www.wetwebmedia.com/dailyq&a.htm tomorrow. Bob Fenner>

Hermit Crabs & Behavior (looking for a new shell or Amore?) Bob, <Anthony Calfo in your service> Quick scenario and question about Hermit Crabs. I currently have a system set up with LR, few fish, Xenia, Snails, & Hermits. I stocked the tank with just 12 Blue Legged Hermits (look identical to and I believe are Clibanarius tricolor) and 6 Left Handed Hermits (Calcinus laevimanus). Today, I noticed that one of the larger BL Hermits was literally attaching itself to another BL Hermit (this one was quite a bit smaller). It was moving its front legs and accessory feeding appendages quite a lot, but it did not appear to be outright trying to extract the smaller BL Hermit. I watched for a while, and another BL Hermit came along and was also watching. The third BL Hermit climbed onto the larger specimen, and finally I broke this up to see what would happen. The smaller BL Hermit that was being 'hassled' was then put at the other end of the tank. About four hours later, the same BL Hermit had found the smaller one - and was performing the same behavior! The same third BL Hermit found them again, and then, one by one, more BL Hermits joined until there were six all in one front corner of the tank. I thought maybe they were hungry and trying to eat the smaller BL Hermit (although, not that small), so I went against my judgment and got some frozen Mysis shrimp. However, when I returned to put it into the tank, the 'party' had somewhat broken up. I fed them anyway, and all seem to have stuck around to eat except the BL Hermit that was the focus of attention. Finally to my question: am I looking at hungry crabs, or some attempt at mating? Good Health, Ryland <hmmm... that depends...were you playing any Barry White or Luther Vandross music at the time? Er,... never mind. The behavior that you have described is not so specific as to indicate mating. They could have just as easily been trying to commandeer a shell...cheeky little monkeys, they do that all the time. When one is about to outgrow it's shell, it gets quite frisky and even tries on smaller shells (I suppose it can't tell until it puts it on!). With hermit crabs of all kinds, it is very important to always have extra and larger shells on hand. Do find and put some in...I wont be surprised if you see a shell change within a week. Do let us know. Kind regards, Anthony>

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