FAQs about Marine Substrates: Size/Grade Related Articles: Marine System Substrates (Gravels, Sands) by Bob Fenner, Marine Substrate Options by Sara Mavinkurve, Deep Sand Beds, Live Sand, Biofiltration, Denitrification, Live Sand, Live Rock, Biominerals in Seawater, Understanding Calcium & Alkalinity,  Related FAQs: Marine Substrates 1, Marine Substrates 2, Marine Substrates 3, Marine Substrates 4, Marine Substrates 5, Marine Substrates 6, Marine Substrates 7, Marine Substrates 8, Marine Substrates 9, Rationale, Selection, Reef  Substrates, By Type: Aragonite/s, Coral Sands, Silicates, Dolomites/TapAShell, Southdown & Such, Collecting Your Own, & Physical Make-up, Location, Depth, Marine Substrate Cleaning 1, Marine Substrate Cleaning 2, Moving/Replacing/Adding To, Marine Substrate Moving/Replacing/Adding To 2, Substrate Anomalies/Trouble-Fixing,

Oolites ("egg-stone") are spherical particles of mostly CaCO3 formed by mineral accretion around a central core.

Smallest Recommended Sand Grade? -- 02/07/09 Hi, <<Hello>> I was researching for sand for a Nano project and I came to this online dealer I trust since I've bought many stuff from him. <<Okay>> I had always believed that the best sand for a reef tank was sugar size sand, it looks good, it reflects the light very well, and it does not trap detritus as much as coarser sand. Or that's what I had understood. <<I am in agreement'¦though the coarser grades can be of use in situations where very high water flow moves the smaller sand grains around too much>> This dealer sells sugar size aragonite, he calls it #1 size, yet he's got a #0 particle size. I asked what it was and he says its aragonite salt sized particles. <<'¦?>> Smaller sand particle than sugar size I had never heard before. <<There are no doubt smaller particles/grains (as evidenced when you rinse the sugar-sized sand)'¦but I did not know such was available graded and in quantity>> I wonder if it's better or worst than sugar size, and what problems or benefits would it have? Hopefully you know something about it. <<The smaller grain size may prove troublesome re keeping it out of suspension or just moving around too much, but also may prove 'more soluble' for contributing to alkaline and bio-mineral content. It's worth giving a try if you want, though I think it might be more suitable to a low flow 'mud' refugium>> Thank you. <<Happy to share. EricR>>

Grain Size For Sand-Sifters - 03/17/06 Hello.. <<Howdy>> I currently have a 90 gallon FOWLR setup with a sand bed consisting of half 1.0 - 2.0 mm and 0.1 - 1.0 mm.  If I had to do all over again I would have all of the sugar-fine sand but what's done is done. <<Ok>> I have read that the larger grain is borderline inappropriate for sand sifter's like gobies and cucumbers. <<Sugar-fine serves best here in my opinion.>> (of course I asked this question to my LFS at time of purchase and they said I would have no problem adding sand-sifters with that grain size). <<Mmm...was it the only size they sold/had on hand maybe?>> My questions is, are there any sand-sifters that would be appropriate for my sand bed or does your experience say I can have the gobies and cucumbers or did I shoot myself in the foot? <<Some of the larger gobies (6"+) may handle your smaller grain sizes fine, but I prefer to provide these animals with fine-grained sand.  Why not add some sugar-fine aragonite to your existing bed?  The goby/Cukes will be able to sift the finer grains, while spitting out what they can't use.>> Thanks in advance and oh yeah.......awesome site! <<Regards, EricR>>

Rubble Rock 8/2/05 I am in the final stages of setting up my 180 gallon FOWLR tank and saw rubble rock at a local aquarium store.  I was thinking this would possibly be good to put in a refugium, What are your thoughts.  If you feel it a good idea can you give me recommendations on how thick the layer should be, lighting, circulation, etc. - D'Wayne <Hi D'Wayne! Thanks for your inquiry, regarding the rubble rock -  it would be just fine to use in your refugium. Keeping a fine grain 3-6" sandbed in the fuge and/or several pounds of rubble live rock is all you need. Depending on your set-up goals, lighting can be used or deleted from the set-up all together. Please feel free to do a search regarding refugium set-ups here. Tons of info, you'll be pleased D'Wayne... - Ali>

Adding more live rock, sandbed and tank Renovation. 7/31/05 Hello again, <Hey Frank!> Ali, I wanted to say thank you for the quick reply! I have a follow up question. I will be following your recommendations to replace the substrate with a 4 - 6" deep sand bed. It looks like the sand you recommended is a 1 to 2 mm grain size. I have heard a lot of opinions on .2 to 1mm sand vs. 1 to 2mm sand. Do you think you might be able to give me your opinion on the different grain sizes and why you recommended the grain size / sand that you did. <Go with the .5-1mm grain sized sand. CaribSea Aragamax Oolitic Select Reef Sand is pretty much the ideal sand for deep sand beds. Several vendors including most 'local reef stores' carry this very popular sand. You have two options here: 1. Siphon out all of your crushed coral substrate, put all live stock in bins, drain the tank, add sand bed, SLOWLY refill tank causing minimal disturbance, wait until the tank is totally clear then proceed to add live stock after careful acclimation. 2. Siphon out apprx. 90% of your crushed coral, leaving just a 1/4-1/8" bed, (covering just the bottom of the tank for aesthetic purposes) and plumbing in an additional sand filter to your tank. For example, a 40 gallon breeder with a 4-6" sandbed plumbed into your existing sump.   Option #2 will be much less work and stress on the animals, however it will require an additional tank (taking up space). On the bright side, you'll be able to keep your nitrate levels in check and the 40 gallon side tank will act as a fully functional refugium as well.> Thank you, Frank <No problem Frank, good luck with the tank renovation. It'll require some careful planning and hard work, however it'll be worth it in the long run. Bust out some cold brewskis and get to work! :) Ali>

Switching my substrate 2/16/04 I am upgrading tanks this weekend from a 50 US Gal to a UK400L (Juwel Rio 400)(US 110?), and wanted to know if I would do more harm then good for my fish by changing my substrate to L/S, from tiny rocks. <many benefits I am sure. We have written about the use of live sand and sand beds (shallow to deep) in "Reef Invertebrates". Tim Hayes of Midland Reefs in the UK is one of our distributors if interested :)> I wish to use the Berlin method to go about doing this. <Hmmm... this speaks to the issue of different folks interpretation of various methods. Conventionally, the Berlin methods is known for bare bottomed tanks, no substrate and heavy skimming. You wish to modify the methods here and add sand at depth? If so, I agree and feel that his is a fine system/style> I know that moving my current substrate will mess with my water readings because of the disruption of beneficial bacteria that rests within the layers, but would it have the same symptoms of a new start by switching to L/S? <not necessarily... assumedly, the majority of your nitrifying bacteria are not in your thin sand bed but in other areas of filtration (filter media, live rock, etc)> Also, if I use some of the old rocks under the sand but above the egg carton foam (and U/G filter) will this help to culture the sand a little better? <not... in fact, do resist the use of the UG/plenum entirely. It has no need or benefit here. A simple static bed of fine sand at 4-6" (10-15 cm) depth minimum will be all that is required> I only have about 3kg of live rock... I know that is not enough... <yikes! yes... frightfully sparse. And indeed an issue regarding the removal of gravel which is perhaps a significant part of your filtration. Let me recommend that you add some foam blocks to a hang on power filter and run them for a month or more before you make this switch so that they accept a large part of the nitrifying load/burden to be carried to the new tank after the gravel is out. You can even slip a foam block on the intake of the filter for extra filtration (great for extending media life in hang on filters)> but I am getting more, and I have at present a Fluval 304 and an Aquapro-1 for filters, (over kill) they will transfer to the new tank for a while, until the built-in filter is established, Plus a 150gal fluidized bed filter, Berlin air-lift 60 skimmer (I have a 150 SeaClone in the mail!) and a 150 gal UV sterilizer. <The fluidized bed filter is arguably more harm than good. It is/will be a nitrate producing machine. Unless you will have a very heavy fish load, this will not be helpful (the fluidized filter). Please also take the time to read through or archives on wetwebmedia.com regarding the SeaClone skimmer and others. Alas, this is a very challenging model to get to work consistently or reliably. And a skimmer is one of the single most important pieces of equipment on a marine aquarium> My fish are as follows- Mated pair of percula clowns, 1 yellow tang, 2 small (half inch at most) 3 stripe humbug damsels, 5 hermit crabs, 6 small/med clear shrimp, and a Silverstreak Anthias (pink). Thanks for your time! Amanda <best regards, Anthony>

Coarse or Fine (Substrate Material Sizing) Howdy, <Hey there! Scott F. here today!> Been recommending this site and your books to all. Great stuff. Decided to turn my old quarantine tank in to a 10G Nano. I already have a few mushrooms in it, and figure I'll add a bit more live rock, an Orchid Dottyback or a Sixline Wrasse and some Zoanthids. Right now I've got about ~1" of course crushed coral in it.  I've read plenty that suggests this isn't the best substrate.  Is this going to be a problem? Should I replace it with fine oolithic?  The tanks pretty shallow so I'd rather not do a DSB. Thanks. Matt <Well, Matt- a lot of opinions exist on substrate materials and composition. The "knock" on coarse substrates is that they tend to trap detritus if not carefully maintained. If you are going with a shallow sand bed (less than one inch), this is probably not a problem. I suppose that the argument can be made (however weak and anecdotal) that finer substrates can provide some denitrification even in very shallow beds. Personally, I like the aesthetics and biological "efficiency" afforded by finer materials, such as the "sugar sized" oolithic aragonite materials. In the end, use what works best for you. If your husbandry techniques are good, it's really a matter of taste. Good luck! Regards, Scott F>

Grain Size Query  I am thoroughly confused over an issue that probably should be simple. I have read two books by two leading authors. One says to use the smallest grain size you can get, preferably down to 1/16th of a mm. The other says no way, use 2mm grain size sand. One says that the smaller grain is excellent because sand bed dwellers can easily move about and that larger sizes are too difficult to move and abrasive for them. The other says that with smaller grain size, there isn't good movement of oxygenated water into the sand bed. The sand I purchased was CaribSea Oolitic Select that is graded to .5mm to 1.02mm. Is that too small of a grain size for about a 3 to 3 1/2" deep bed? I can't go much deeper because of the built in overflow slots on my tank.  <I see the dilemma- is there a way that you can block off the bottom overflow slot? Otherwise, I find grains of the range .5mm-1.00mm the best for feeding your tank naturally! It will help produce great zooplankton, and would be good for a variety of macroalgae. The only problem I foresee is that this grain size has a half-life of about two years- so you'll be down to below 2 inches by 2006. You're going to need to stay on top of this, because "in this mid range, the sand is often too deep to be wholly aerobic and yet not deep enough for efficient denitrifying faculties.">  <quote from article: http://www.wetwebmedia.com/deepsandbeds.htm >  Thanks!  Sand Silly <Not a problem, Ryan> 

Playing With Sand Thanks again for the quick response. Would you put the sand bed right over top of my existing substrate (florida crushed coral, already 3-4")? <Well, there is a lot of controversy over sand grain size, etc. If you're gonna use a fine, oolithic aragonite, it's probably best to gradually replace one section of the tank substrate at a time, letting the process take a few weeks, IMO> And what about vacuuming the substrate after the sand bed is installed? Can it be vacuumed and is it necessary? <I would not disturb anything more than the first 1/2 inch or so of the sand bed. If you are a careful feeder, and are conscientious about maintenance, you may not really have to do much of anything to maintain a healthy clean sand bed> (I assume when you say sand you mean live sand?) <Yep> If so, any recommendations as to which type? Chris <I'd go for a nice, clean grade of sand from Fiji or another South Pacific locale. Your LFS can probably recommend some. Good luck! Regards, Scott F>

Reef Sand Hi Anthony or Steve, love the site. You guys are doing a great job in Bob's absence. <Thank you... but Bob is only absent in mind... not body...hehe. Anthony> Here is my question. I have a 2 year old reef tank that is up and running fine. I currently have crushed aragonite and was thinking of switching to sand to make the tank healthier. <agreed> Should I do this or leave well enough alone. <coarse media is more problematic long term. Fine sand has numerous attributes... not the least of which is denitrification of you fill at more than three inches deep> If I change, should I do a portion of the tank or all at once?  <rather laborious either way... with fewer/hardier livestock, I'm inclined to stress them once with a big but well planned complete change over... rather than repetitive insults> Currently I have about 45 - 60 lbs of live rock in my 55 gallon tank. <you might even add some more fresh live rock> Thanks for your help. Ray <quite welcome. Anthony>

Sand Beds... Since I need a QT tank I am moving everything from my 29 gallon to a 37 gallon that has been drilled for an overflow and in the process will install a 10 gallon sump.  The 29 has about 30 lbs of live rock and about 1 ?" of Carib Sea Aragonite crushed coral.  Since the tank is much taller, I would like to make the sand bed 3"-4" for de-nitrification. Should I use fine Aragonite sand mixed with the coarser sand already in the tank or stick with the same size crushed coral that is already there? The tank has been up and running for about 5 months.  Also, do you see any advantage to installing a Rubbermaid tray into the sump and making into a small refugium? <Wow! Your intentions are great- everyone should have a quarantine tank. In regard to the 37 gallon system, I'd recommend that you use all of the same grade of sand. It's possible, but not recommended, to mix drastically different grades of sand IMO. Usually, a 3-4 inch sand bed is best constructed of finer grades of sand (oolithic aragonite, like CaribSea's "Aragamax Sugar Fine Sand". Coarser grades, including crushed coral, can create detritus traps in your main tank. Also, many of the beneficial infauna, such as worms, can actually be shredded by the coarse stuff! Why not use the coarse stuff in your planned refugium? In a Rubbermaid "refugium", you'd probably be able to have a gnarly copepod population with that coarse stuff! Good luck! Scott F.>

Size Doesn't Matter? (Mixing Sand Grains...) Hi, been a long time reader and a great fan. I figured I'd ask all my questions at once and get them out of the way. First off, do I need mechanical filtration in a reef tank if I have a large amount of live rock, and good skimming? Can I get away with Vacuuming and water changes? <It's not necessary, particularly if you embrace good husbandry practices. However, you may want to use "passive" mechanical filtration, such as micron "filter socks", etc. to help trap gross particulate matter, etc. Just clean and/or replace them regularly.> I have a fair amount of micro bubbles in my display tank ... after much searching, I realized that I may have two much water flow? <You can almost never have too much water flow! However, you may have some air getting in somewhere, or something anomalous in the return plumbing causing the microbubbles...> I have a 125 gallon AGE tank with built in overflows in each corner, being serviced by two Mag 12 pumps... I noticed that when I turned one off, the bubbles went away almost completely. I have one powerhead in the tank right now, Hagen 802 I think... and I plan on adding another this week. My question is, could I just use one pump for the tank, or should I get two smaller pumps. <Well, it's really up to you. Of course, the electrical consumption and heat are factors to take into account. I suppose I would rather use one larger pump and bled it off into several outlets...> How long is too long for quick filters for the Hagen power head? <As far as how long between media replacement? These things can accumulate detritus and other stuff that can degrade water quality over time. I'd consider changing or servicing them every two weeks...Or more often, if needed> I've read that mixing types of sand substrates can be bad? How bad? I have small grain sand bed (step up from sugar fine) about maybe 1-2 inches deep, with another 1/2 -1 inch of medium course sand (little less than sesame seed sized) on top. I also have a few sporadic rubble and shells about. <There is a lot of difference in opinions out there regarding uniformity of substrate materials. In my humble opinion, and experience- as long as you're maintaining good conditions in the system, and as long as the depth of your substrate is 3 inches or more with relatively fine grain size, you can mix different, yet similarly-sized sands without much concern. Depth is a more crucial factor than uniform grain size, IMO.> Tank is 125 gallon AGA 30 gallon sump w/refugium 120 lbs of live rock small fish load (2 clowns, 1 Dottyback, 1 Firefish, 2 gobies) a bunch of hermits and cleaner shrimps. 2 Mag 12 pumps, with a massive aqua -c skimmer powered by another Mag 7 <I like the massive skimmer concept!> Thanks! Miguel <My pleasure, Miguel! Regards, Scott F.>

Mixing sand grains Hi Guys, <Harrow> Quick question please! I have a med sized sand (CaribSea Aragonite) <ech...> and bought additional sugar sized  <woo-hoo> Is it okay to place the sugar sized over the med-size?  <not recommended if your goal is denitrification (all fine for that). If not, please at least add screen between layers with course grain on the bottom> My plan is DSB about 6" deep.  <excellent!> Thank you guys you're doing a mighty fine job of educating us. <thank you for saying so, good sir. Anthony>

Non-sand bed thickness ?? I have a 29 gal salt aquarium with ~ 3 inches of crushed Florida coral.  <Yikes!!! A scary detritus trap... any dreadful algae growth in the tank because of this nutrient sink?> Most of the pieces I can see are fairly large coral or whole snail shells that average 1/8" to 1/4" across. I have read on some of your other FAQs that using between 1-4 inches of sand bed depth may cause long-term problems. Is this also true of the coarser substrates like mine? <especially true of coarse substrates!> I would also like to adapt my substrate for NNR. Would adding 1-2 inches of fine aragonite substrate work with the existing crushed coral underneath, or should I look at replacing the CC.  <alas... mixed grain sizes are problematic. NNR with a deep bed of sugar fine sand. 5+inches gets my vote> BTW, I just started a 10 gal refugium with 20 lbs of live sand, 3 lbs of live sump rock, and some Caulerpa. Is it still worth the effort/expense of trying to set up NNR in my main tank's substrate? <likely yes... most display tank bio-loads can burden a 10 gallon refugium no matter how efficient it is> Thanks, Darrell <Always welcome my friend. Anthony Calfo>

Mixing marine substrates Thanks Bob for the blazingly fast response! One can almost think you wear your computer around with you. <Have been accused as being a device itself> You mention mixing the two substrates and indeed I thought of that. But wouldn't the finer sand find its way to the bottom defeating the purpose? <Yes, depending on which one is actually more/less dense, a greater proportion of the one mixed in below/above more> If that isn't a big deal, then I will begin the process tomorrow. <Not that big a deal. Bob Fenner> Zimmy

Marine fish Hi, Bob. Can you tell me good web site that shows pictures of marine fish including a short description of them (length, adaptability, etc).  <Wish I could... I use Scott Michael's Pocket Guide and Reef Fishes books, the old WEB/HRA/RayH TFH Atlas... and a bunch of other references... oh, including fishbase.org on the Net...> I just love Your web sites. If I put 1" coral gravel in the tank that is big enough in size to be washed with a gravel cleaner without being sucked up, what size would You recommend by No.? <Five> I found web sites that sell gravel sized by No. From 2-20. I see that anything above 10 is too large but between 2, 3, 5, I can't distinguish the size of the pebbles. I have to tell my dealer the size by No. so that he can order it. Thanks, Bernd <I understand. Bob Fenner>

Hard time with (substrate choices for marines) Hello Bob, I am reading lots of your material, but this time I have a friend that is in the medical field and knows the different values and chemistry. I am starting to make more sense of the chemical balance. <Sounds good> I am also trying to take control of the green hair algae and green algae that covers my glass daily. I have added some Cerith and some Nassarius snails. My question is: I used Seaflor Aragonite Reef Sand, which is rather course. Is this a "fine" enough sand bed for the Nassarius or should I add some find grain sand to the bed? <Finer would be better for them. Bob Fenner> Thank, Dave

Substrate materialBob , I currently have a 120 with about 40lbs of fine powdery marine sand as substrate (1/2 - 3/4 inch). I have a fish that sifts this and the sand gets deposited all over everything . What do you think about adding 40 lbs of a coarser substrate over the top of the sand. Thanks, Odlaw <Sounds like a good idea... the two will mix (of course)... but as long as there's enough space/volume for the smaller material to settle "in between"  you should be fine (pun intended)... with much less settling problems. Bob Fenner>

Substrate particle size Hi again, Well this is kinda off subject, but the sand I have in my tanks now is aragonite which is about 2-3mm in size. I have read in a variety of places its better to have sugar size sand (oolite?), so animals can burrow into it. I have also heard that there is a sand that hardware/home stores sell that can be used in the tank, which I'm sure is cheaper than buying it at the LFS. Have you heard of such a sand, and if so what is it called :). Thanks. Chris >> Hmm, I'd like to know what this sand is... at the hardware store... Most all I've ever seen are silicates (kiddie play box sand), metamorphic chondrites ("gravel" for freshwater), and maybe flints (good for some freshwater systems)... maybe dolomitious material or Tapashell (mainly calcium and magnesium carbonates) you could find at such outlets that were in "farming" areas... And, nah to the finer substrates (oolithic... fine, dusty stuff)... as being better... they have their own sets of problems. You're better off with the 2-3mm stuff of all about the same grade... Maybe place the sugar stuff in a refugium... Bob Fenner