Corydoras slowly dying off one by one, no one has answers.     4/22/20
Hello. I am reaching out to you with a very strange problem that no one else seems to have any idea on what it could be.
<Understood.>
This involves my Bronze Corydoras, who all came from a clutch I hatched in June of 2018.
<Well done on the breeding, by the way!>
Before I go into the details of the problem, I'll do the important housekeeping of tank parameters. It's a planted 75 gallon, set up since February 2019, with plenty of caves and nooks for hiding. Substrate is a
fine gravel that they have no problem with, all have full bellies and long barbels.
<Still, as you seem to recognise, not ideal.>
Tankmates are 2 adult Bronze Cories, 4 Peppered Cories (I need to get more) and 15 Cherry Barbs.The problem has gone on for a long time though, so it is unrelated to tankmates.
<And Cherry Barbs are lovely fish that shouldn't cause any problems.>
Ammonia: 0ppm Nitrite: 0ppm Nitrate: 20ppm pH: 7.8-8.0 (I added driftwood yesterday, so this might change in the future.) Temp: 74-76F
<A little on the warm side for this/these catfish. Peppered Corydoras especially are low-end tropicals, even subtropicals, and thrive if given a cooler winter period. Around 18-22 C/64-68 F is ideal. Supposedly, wild fish can be found swimming under the ice on rare occasions! Bronze Corydoras are not quite so fond of cold, but still, I'd be keeping things towards the cool end of the range, maybe 22 C/72 F, and providing plenty of oxygen. Yes, the species is very adaptable, but if you're struggling with a
certain species, sometimes going back to basics, and seeing what "ideal conditions" would be can help, at the very least, in the dismissal of factors that aren't to blame.>
GH: 8-12 KH: 4-6
<Wouldn't expect much of a pH change with this much carbonate hardness, assuming regular water changes.>
Water changes: Weekly, 20%-40% depending on what is needed. Filtration: Marineland Penguin 200, Cascade 1000 Canister filter, a sponge filter
<All sounds fine, but how much water movement is at the bottom of the tank.
Put some flake down. Does it sit there? Or flap about weakly? Or is it quickly whooshed away in the current? Remember, slow water movement at the bottom of the tank means low oxygen levels. Not an issue for midwater barbs and tetras, which swim into strong water currents instinctively, and so get
more oxygen. But benthic fish, such as catfish and loaches, may struggle.
Sure, they can swim to the surface to gulp air, but that's not something most species are meant to do all the time, and indicates they're under a degree of stress.>
Treatments: Seachem Prime, Aquarium Co-op EasyGreen Food: Once a day feeding of any combination of Hikari Sinking Wafers, Omega One Catfish Sticks, Omega One Sinking Pellets, and Hikari Micropellets. Once a week I feed thawed frozen Brine Shrimp and Bloodworms, Omega One brand. Occasional treat of blanched veggies for them and the Cherry Barbs.
<All sounds fine.>
None of the other Cories have developed this, just these siblings. The symptoms are always similar. The Cory becomes lethargic, looses its appetite, and breathes rapidly. They often become dark in color and
sometimes, but not always, their eyes cloud over and they loose vision.
They never live for more than a few days after the symptoms first present.
It only ever effects one Cory at a time, and there's always a period of time between one showing symptoms. I don't believe it's related to water quality or diet, their foods have plenty of Vitamin A and I'm diligent about keeping things clean.
<But do see above re: water movement and oxygenation. If midwater fish are healthy, but you're losing benthic fish, that's a good clue there's something amiss "down deep" and your attention should be directed there.>
I've speculated that this is some sort of genetic problem. Their parents were chain pet store fish, and though their mom has always been very healthy, their dad was not the most robust, and he passed away without any cause or symptoms not too long ago.
<That can certainly be an issue, but if genetic, you'd expect to see deformities from the fry-stage onwards. While poor genes can indeed mean a weaker immune system, again, you'd expect to see this from the get-go, not months or years later. So while certainly a possibility, it would not be my first choice for an explanation.>
The fry did not have a good survival rate, and there were genetic abnormalities noticed in some of them as they got older. (Mainly, some of them developed very long fins, and all of those died from this condition.)
<Long-fin Corydoras are "a thing" in the trade, and yes, the inbreeding does make them a bit more delicate. Usually they're more prone to Finrot and other such afflictions of fish easily damaged or nipped.>
They also are slow growers, at nearly 2 years old they are nowhere near adult size.
<Odd.>
I'm down to 11 from over 30 juveniles that grew big enough to put in with the adults, most of them dying from this issue. I have yet another one who started showing symptoms last night. This Cory was absolutely fine the day before.
<Not good.>
At different times for different fish I've used Furan-2 and Amoxicillin in a 10 gallon quarantine tank. The fish always died overnight or the day after treatment. I have tried quarantining some of them and treating them with antibiotics, because the symptoms show some similarities to a bacterial infection, but they always die within a day or two of starting treatment. It seems like whatever this is, by the time symptoms show they're too far gone to treat.
<Understood.>
I'm at a complete loss here, I've asked other places and no one has any idea other than complete shots in the dark. This has been very hard to deal with, and I feel completely helpless. If anyone has any idea what this could be, or knows someone who might, please let me know.Below are images I've taken over the course of many months, in chronological order. Each one is of a different Cory who had this condition, the last one is currently suffering from this. The first one is one of the long fins I mentioned
earlier. I'm linking them because the images are very large.
<Appreciated.>
https://i.imgur.com/ALKc5MA.jpg
https://i.imgur.com/4Smpjb4.jpg
https://i.imgur.com/QlrQvDg.jpg
https://i.imgur.com/Zxs24th.jpg I appreciate any help you can give me. If you need any more information, I'm happy to supply it to the best of my abilities. - Adam
<Adam, my instinctive feeling is there's something environmental going on here. Get back to me when you've done the flake test on the substrate. If the water is rather still, I'd go with long-term oxygen stress, which combined with the higher than ideal temperature, could make the fish more
prone to opportunistic bacterial infections. I mean by that your fish are almost certainly dying from something like a Pseudomonas, Aeromonas, or Mycobacteria infection, but all of these are latent in even the best aquarium, and only cause problems when the fish's own immune system is compromised. Mycobacteria infections are notoriously difficult (i.e., impossible) to treat, but then again, even the more easily dealt with Aeromonas infections aren't going to go away if too far gone or the environment keeps the fish under stress. Cheers, Neale.>
Re: Corydoras slowly dying off one by one, no one has answers.    /RMF     4/22/20
<<Hi Bob! When you paste this up, can you add any thoughts of your own? I'm very open to ideas here! Neale.>>
<Sure; have read over, incl. your reps. First I would ask Adam to "check the checkers", to make sure the test kits (particularly ammonia and nitrite) are accurate. When the aquarist stirs, disturbs the substrate, do gas bubbles erupt? Is there a soil substrate mixed, in place? Are they using a liquid plant supplement?
Foodwise, I'd skip the bloodworms entirely and the blanched vegetables for now.
I too suspect the cause of these losses as environmental, perhaps with a genetic component.
BobF>
Re: Corydoras slowly dying off one by one, no one has answers.      4/27/20
Hello! I apologize for not responding sooner, I did not see that you had posted a response until today.
<Curious; you should have received a copy of my response in your email box.
Maybe check the spam folder?>
First I'll answer the questions and concerns that were brought up.
<Cool.>
To begin, the water movement. There's a good amount of flow all throughout the tank. All of the plants in the tank sway gently from the water current, including the low laying plants and their roots. Sinking foods roll around across the substrate during feeding times.
<Good.>
Sometimes I feel like it's too much flow! But I decided to do the flake test anyway as you suggested. I tried it out in several spots, and the results were about the same. Most of it was immediately whisked up by the
current, and the pieces that did stay on the bottom flapped and rolled around. That is, until the Cories ate them.
<All sounds fine.>
I also have both a sponge filter and an airstone going at a strong pace, so there's plenty of oxygen. They do surface for air on occasion, but I wouldn't consider it excessive at all. I'd say maybe 1-3 of them out of the
16 total will surface in the period of an hour.
<Normal.>
And they don't stay at the surface either, they dart up for a quick gulp and then right back down.
<Good.>
For the substrate, it's CaribSea Peace River gravel. I actually have Black Diamond Blasting Sand purchased because I want to switch it out, I find the gravel ugly and my Cories will appreciate sand.
<Blasting sounds like sharp sand. I'd be leery of using that with any bottom-dwelling fish.>
But I've been worried about the stress it would cause them. If you think it would be beneficial to do it now, I will go ahead and switch it next weekend. There isn't any dirt, root tabs, or anything else in the
substrate. I never see gas bubbles, and the substrate is pretty thin. (I didn't buy enough originally, part of why I want to change it.) I do use Aquarium Co-op Easygreen liquid Fertilizer, but my Cories were having
issues even during periods when I didn't use it. I've also never heard of anyone having a problem with fish related to this fertilizer, it's a pretty mild fertilizer. No copper in it or anything. I might stop using it
temporarily though just as a hail Mary.
<Understood, and a wise approach. Plants will go months without fertiliser, and even switching off CO2 fertilisation, if used, can be useful if you're trying to figure out an underlying fish health problem.>
My test kit is the API Freshwater Master Test Kit. 2 years off from expiring. I've previously checked it using my tap water and test strips to compare, and it seems to be accurate.
I was surprised to hear that my water is too warm for the Peppered Cories.
Most resources seem to point to 78 degrees as the maximum temperature they can be at.
<Maximum, sure; but bear in mind that's a range, and in the wild they're be experiencing much cooler winters. They're a subtropical, not tropical, fish, from a more southerly part of South America than the usual Corydoras species we keep as pets. While they're extremely tough, if you're having health problems, it makes sense to ask yourself: Am I doing anything to them that isn't within their normal tolerances? Might be temperature, water chemistry, even diet.>
But the Peppered Cories haven't had any problems at all. I also should have clarified, it only reaches 76 during the hottest months of the year, when the ambient temperature in the house goes up. It's at 74 degrees for the majority of the year.
<Understood.>
One weird new thing, I've noticed all of my fish (not just the Bronze Cories) have been flashing on occasion. Not exclusively, but I usually never see that behavior, so it's odd. Only change to the tank is that I
added a piece of Mopani driftwood in last week. It was boiled, allowed to dry, soaked for several weeks, and allowed to dry again before being added.
Hasn't leached much tannins at all and hasn't really changed the pH. All tests came out normal, in the range I described in my first post. I've never seen it in the previously sick Cories either.
<If the Mopani is from a reputable source, i.e., an aquarium shop, it should be fine. Bogwood bought off eBay tends to be a bit hit-and-miss, though. Collecting your own wood, while do-able (I certainly do use locally
collected wood at times) always carries a risk. If in doubt, remove.>
I'll increase the oxygen and do a large water change today, just in case.
This is so frustrating. It feels like the more I care about this tank, the more time and attention I give it, the worse things get. I do so much research, I love helping others who have problems or questions. But when it comes to my own tank I feel like a complete failure.
<Sometimes, I suggest to people they just accept certain fish species don't work for them. It might be their tank size, their local water, the way they maintain the tank. Who knows? But whatever. If one Corydoras species does fine for you, but the other doesn't, then don't bother keeping the difficult ones. If midwater fish are happy as Larry, but the catfish are struggling, then maybe don't bother keeping catfish for now. I know that isn't a very satisfying answer, but fishkeeping isn't a competitive sport, and if it isn't fun, what's the point? The alternative is this: Strip the tank down to bare basics. Remove everything but clean washed gravel, the filter, the water, and the fish. Perhaps a few floating plants or plastic ornaments for shade. But basically a bare-bones system. See what happens now. Remove anything messy, stir and clean the gravel, optimise the filter.
Leave it running a few days or weeks. Do the fish look better now? Then start rebuilding the tank you want, but using new rocks, wood, and plants -- or at least being a lot more selective about what you add, to minimise the risk of contamination. Ask yourself each time you put something in the tank: does this look safe? Rocks can have metal seams, bogwood can be decaying. Plants are usually fine, and while they don't like being uprooted to a bucket of water for a few days, they should survive.>
- Adam
<Cheers, Neale.>

Cory lump     9/22/19 Hi can you tell me what this lump is and how to treat? I’ve had him for 2 years. The only change to the tank is I bought a new plant about a month ago and found one snail from the plant. Water perimeters are good. It’s a 20g tall tank with live plants. I feed every 3 days. I have lava rock and a sponge filter on the intake. I do a 50% water change monthly. I have a gourami and a rubber lip Pleco and some shrimp. All other fish are ok besides the Cory. Thanks Kelly <Hi Kelly. This may be a blister, may be a tumour. Hard to say from these photos, or really, from anything short of a thorough examination. Blisters tend to be associated with reddish bacterial infections and show signs of dead skin around their edges, whereas tumours often grow from deeper inside the fish, pushing outwards, but otherwise have the colouration of the surrounding skin unless actually so large they're stretching the skin. Blisters are caused by a variety of things, but abrasions with coarse sediments and rocks are the most likely if on the underside of the fish. Treating as per Finrot can help, but the main thing is to fix the sediment by replacing with something more catfish friendly. Smooth lime-free sand is the ideal for Corydoras. Do also ensure there's adequate water flow along the substrate. Pop a bit of fish flake there and see if it gets shoved along briskly. If not, there's likely pockets of still or sluggish water that can stress bottom dwelling fish like Corydoras, and this in turn can manifest itself in the form of Finrot-type infections. Review, and act accordingly. Cheers, Neale.>

Cory’s      6/5/19
My female Cory has a yellow spot on her top fin, she has always been very active, and still is, what could it be
<Hi, could be many things, can you please send us a pic?... will be far easier to id the problem. Wil.>

Corydoras Keep Dying      12/12/18
Good Morning!
Long time reader, first time writer. :)
<Welcome!>
I have a 40 gallon breeder that can't seem to keep cories alive. I've lost small batches of sterbai (5) and bronze (6), and now I'm afraid I'm going down the same road with pandas (started with 12, down to 10). Other fish seem unaffected, and a common symptom appears to be air/gas in intestines.
Am I missing something?
<Likely, so...>
The tank:
40 gallon breeder, 36" x 18" footprint, black blasting sand substrate (well rinsed), temp was at 79-80 for the sterbai/bronze, close to 76-77 for the pandas.
I have a cascade 700 canister filter and 2 sponge filters.
Livestock at this time includes the 10 pandas and 2 Apisto borellii (1-1.5"). Nothing else.
Some hardy plants, a few driftwoods, and some IAL and oak leaves.
<Whence came the pieces of driftwood? If purchased, are you quite sure these are "aquarium safe?" Many sold for reptiles are not safe for aquariums. If acquired from the great outdoors, how did you cure/prep the pieces? At this point in your story, I suspect the driftwood, but I will read on...>
Timing:
Started the tank in mid Sept, with half a dozen small pentazona barbs.
Cycled tank with media from another filter.
On Halloween, I added 5x 1" sterbai cories. The following Friday (2 days later), in the afternoon, 2 were floating upside down, then 2 more shortly after. Those 4 died within hours, 1 survived.
<Yikes! Something is seriously wrong here. How did you introduce them to the system? Did you acclimate them to the new water conditions? Did you test the water from the pet fish shop?>
I know everyone reaches for sbd in situations like this, but I autopsied 3 of the dead fish,
<?!?>
and the intestines were full of air.
<Well, yeah! There is this thing that happens after an organism dies. The resident bacteria have a blitz and produce gases as they ravenously digest their now deceased host. It will happen to you too some day, and to me.>
Some food (not much), but intestines were full like those long balloons clowns make shapes from. No other symptoms.
<...that you could see or recognize with the "naked eye.">
Granted, they're small fish, and seeing anything can be hard.
<If you intend to continue filleting your deceased pet fish, I highly recommend investing in a good microscope. Much to be seen can't be seen without one.>
The lone survivor (which also had buoyancy issues, but never to the point of floating/dying) was quarantined for 4-5 days (no meds, since no diagnosis),
<A good policy>
and seemed to stabilize. But 3d after being returned to the main tank, it also died,
<Interesting>
and again it appeared full of air. I should note that the autopsies were done shortly after death, and all of the sick fish were very buoyant before they died
<This can happen for any number of reasons. It is a very non-specific symptom - a sure indicator of poor fish health, but with a lengthy differential diagnosis.>
(i.e. I don't believe the gas in intestines was a post-mortem symptom).
<Impossible to know for sure either way.>
Through all this, the pentazonas were fine. Ammo/nitrite were 0, nitrates were 5-10.
<Ok>
On Nov 6 I added half doz bronze cories (I admit to getting them as coal mine canaries; clearly this tank can support fish, but can it support cories?). All 6 died one by one over a 2-3 week period. No outward
symptoms (well, except dying). Frustrating. And they had started off so well in my tank, foraging deep in the sand, very active. These did not float when they died.
Through all this the pentazonas were fine. Again, parameters good.
I rehomed the pentazonas to a new office tank, and the tank stayed empty for about a week.
Then on Dec 4 I got a dozen 0.75-1" panda cories, added them, along with a M/F Apisto borellii.
<That is a lot of fish to add all at once.>
They seem to be great tank mates, same pace, feeding rate, temperament etc.
All has been good until last night (Dec 11), when 1 was floating (air in intestines again), and another this am (didn't check). As of Sunday when I did a whack of testing, parameters generally good; ammonia was over zero,
<Yeah mate, I think you added too much too quickly to a "dormant" system.>
but under 0.25 (I've been feeding liberally, though, so that might be it.
<Yes, that too will do it. I would stop feeding for a few days at least.>
I dosed with Prime, haven't re-checked yet), zero nitrites, nitrates under 20.
<Prime is a one-time "band-aid" type fix. It binds the nitrogen cycle products so that these get taken up in the filter. If you don't keep adding it, the problem will return unless corrected some other way.>
Other pertinent:
I feed good quality food, and lots of variety. Thawed bloodworm, mysis shrimplets, bbs. Crushed Spirulina flake, regular community flake, Hikari mini wafers, Fluval bug bites.
<Maybe too much though?>
My tap water is moderately hard, so I have been mixing the water for this tank with RO/DI at about 3:2 (RO: tap). That's giving me dGH of 5-6 (100ppm), and dKH of ~4 (~75ppm). My pH remains around 7.5 (hard to tell, since it always appears to lie right between the high end of the normal pH test, and the low end of the high range pH test).
I'm using a perpetual drip and overflow to keep new water running through tank, rate of about 1.5g new water per day. And I vac as necessary.
<As necessary? How often is that?>
In summary:
Why do mid level fish appear to remain healthy and fine, while bottom dwelling cories are dying?
<Very different species have very different sensitivities, ability to tolerate physical and/or physiological insults. I suspect the problem here to be either trauma from transport/introduction or a toxin coming from
somewhere as of yet unknown. Do see other similar recent queries here:
http://www.wetwebmedia.com/FWSubWebIndex/CoryDisF4.htm >
Are there any diseases/infections/conditions that are known to cause gas in the intestines as a primary symptom, i.e. not post-mortem?
<Again, floating and bloating is just too common a symptom - like headaches and nausea in humans - could be from anything!>
Any suggested interventions? Shelled peas? Epsom salt in tank, or as bath?
<Do read other query answers in the link above. I suggest removing the driftwood, adding carbon, looking for other potential sources of toxins... also be sure to follow good acclimation protocol.>
Many thanks for your time and consideration!
<My pleasure.>
D
<Cheers Sara L>
Ontario, Canada
Re: Cories keep dying      12/14/18
Good Morning,
<Buenos dias>
So fast with the reply, thank you!!
You've focused in on a few things I did not think are important, and aren't placing much weight on things I've been clinging to. Which is why I have asked the experts!
<Haha, wait, who told you we are experts?>
To put me straight, so to speak. :)
The driftwood: 1 large piece, collected from a local headwater stream (no ag runoff or pollutants).
<Yeah, right... that you know of or that has been reported/documented.>
There are brook trout in this stream (maybe other tiny fish?). The wood was allowed to dry for about 6 weeks, then boiled for 20 min.s. In any event, I'm more than happy to remove all possible problems,
<I do strongly suggest you remove the piece collected locally. It's just too much of an unknown and a likely source of something troublesome. Even if it is not a toxin from runoff/pollutants per se, there could be something else (some tannins maybe) leaching out of it.>
and work from there, so I'll pull it out tonight. There are also a couple of smaller pieces I got from a local aquascaper, vine wood he imported by the crate, and it's used in many tanks by many local keepers.
<If removal of the large local piece doesn't solve the problem, I would remove smaller ones these next.>
Carbon: Great suggestion, I missed that. It will go in tonight.
<Never really hurts and often helps!>
Acclimation: floated sealed bag for 20 min.s, then add small amounts of tank water over 1hr (pour out half of mixed water half way through), then add fish to tank via net
<Nets are terrible (too much risk of injury with them getting stuck/tangled). Personally, I avoid them whenever possible. In my opinion, it's better to scoop them out gently by hand than with a net, or just pour them out with the last little bit of bag water.>
without any store water. But deaths have all occurred after at least 2 days, and now upwards of a week - is that consistent with insufficient acclimation time?
<Based on the technique you described, no, I doubt acclimation was the problem. As for how injury from poor acclimation might manifest in the fish, that can vary greatly.>
I've never found an answer to this.
Store water: not tested, but I believe it has similar pH and hardness to this tank. Regionally, our water is quite similar from one municipality to another (medium hard, well buffered). It's definitely not polar opposites.
Dormant tank: during the week the tank was dormant (before I added the 12 pandas and 2 Apistos), I kept feeding the tank with crushed flake (using the same amount as I had been feeding when it had fish).
Adding too many fish: In my own defence, the tank/filter was still cycled when I added the fish, the cories and Apistos are all very small, and for the bioload, it's a big tank. I haven't been testing daily, but none of the fish (past or current) showed any signs of irritation/stress like gasping, flashing, hiding, pumping gills, and so on.
<Ok>
Vac "as necessary": I keep my tanks pretty clean. Most have sand substrates, which require less maint than gravel. I vac when there is visible detritus in areas with less flow. At any rate, I never go more than
2 weeks between vacs, and "water changes" are constant with the drip through system.
Prime for low ammonia reading: I know this is a 24-48hr band aid, and if the source of ammonia, or lack of processing ability aren't addressed, the problem persists.
Rate of feeding: I'm generally conservative when feeding my tanks, but I have a soft spot (fear spot) for new fish. Cories are such casual feeders, I'm fearful that the 30 second or 2 minute rule won't give enough food.
<Do reduce your feeding. Fish do not need as much food as people tend to think they do. Also, they can go a very long time (we're talking weeks) without any food at all.>
Even with the filter off, some foods don't even settle to the bottom in that time. When I listed all the foods I feed, I should be clear that it's not all at once. One at a time only. For flakes or other dry food, a
smaller-than-medium thumb-and-one-finger pinch is all. For frozen foods, less than half a cube of bloodworm, or maybe a quarter of a portion of mysis. At any rate, I'll fast the tank for 48hrs, dial back the feeding after that, and monitor ammonia carefully.
<I think if you remove the drift wood and add carbon, you will likely see an increase in your Cory survival rate.>
Cheers,
David
<Good luck! - SaraL>
Re: Cories keep dying      12/14/18
Thanks again, Sara. Driftwood out. Carbon in. No food. I'll keep an eye on things.
<Great. Do start feeding again in a couple of days though. :-)>
Also of note: Like many fish folk, I rarely test except when something is wrong (that I can see or sense). But with this tank, I've been keeping on top of parameters a bit more diligently, given the problems I've had.
<It's always a good idea to test every once in awhile, problems or no problems.>
I mentioned in a prior email that I am seeing trace ammonia. I've had a chance to check other tanks and tap water, and I'm getting a trace reading across the board. Best match for colors is between <0.25ppm for tap and other tanks, and >0.25ppm for the Cory tank. Even my RO/DI is testing at >0ppm. So I'll look into an ammonia removing media for the filter, and continue to use Prime and monitor.
<Sounds like a reasonable plan.>
Cheers,
David
<Cheers, Sara L>

Undecided about how to treat further     10/18/18
Hi crew!
I originally added 7 peppered Corydoras to a filtered and cycled quarantine tank. They have been in there for almost two weeks (I plan on quarantining for 4 weeks).
I purchased them from a local chain fish store. They told me that they had been treated with Quick Cure for about a day while in display tank.
<Mmm; the ingredients are too harsh (formalin, Malachite Green) for Corydoras, most catfishes>
My tank parameters are 0 ppm ammonia and nitrite, 5 ppm nitrate, pH 6.8, temp 76°F, Aquaclear filter and airstone, sand substrate, driftwood and wood stone.
<Sounds good>
I lost two corys the second day after I added them to my quarantine tank. I did carefully acclimate them and they didn't seem stressed afterwards. I don't normally add medication to the tank unless I notice a problem. The second morning one of the corys had severe pop eye in both eyes. Eyes were not cloudy but were severely swollen, one eye had actually ruptured.
<?! What happened here? Something/s very wrong... too much difference twixt the waters? The fish too long in the bag, overheated...? Some source of overt poisoning? I'd removed the driftwood, add activated carbon to your filtration>
A second Cory had mild pop eye in both eyes and a third was on its side breathing rapidly (no pop eye). The Cory with the severe pop eye died that morning as did the one on its side with respiratory issues. I did a small 15% water change (parameters were normal) and dosed the tank with Kanaplex. I did a full three dose course of Kanaplex, then 48 hours after the last dose did another water change (25%) and have basically just been observing for further symptoms. The Cory with the mild case of pop eye recovered completely and up until today everyone has been eating and acting normal. I did have one that was away from the group quite a bit and not as active but still coming out to eat.
This evening when I got home, one of my corys (I believe the less robust Cory) was basically floating near the surface; still alive, he will swim a bit when nudged, but not looking well. No sign of hemorrhage under skin, body normal with good slime coat, fins and barbels normal, respiration normal but extremely lethargic and just floating at surface. Upon inspection he looks perfectly normal. The remaining 4 corys are eating and acting normal.
I do have Metroplex on hand as well as General Cure. Do you think I should try adding Metroplex to the water column or food?
<I would not. Metronidazole has specific uses. Unless you/I can detect the organisms involved (if any; which considering the rapid onset...) I would not treat>
I do a water change every 5 days (tomorrow is 5th day) but even though I match pH and hardness and temp, I'm afraid a water change will push the sick Cory over the edge. Although the antibiotic appeared to resolve the original problem, I don't want to repeatedly dose the tank. I'm wondering if there could be an underlying parasitic problem (gill fluke?). None of the corys look emaciated and even the sickly one has a normally rounded belly. Any suggestions?
Thanks crew!
Sue
<Corydoras paleatus is a hugely aquacultured species of long use; quite labile in its placement, range of conditions. Again, I suspect either trauma or toxicity at fault here. Would just remove the driftwood, add carbon... Bob Fenner>
Undecided about how to treat further     /Neale     10/21/18
Hi crew!
I originally added 7 peppered Corydoras to a filtered and cycled quarantine tank. They have been in there for almost two weeks (I plan on quarantining for 4 weeks).
I purchased them from a local chain fish store. They told me that they had been treated with Quick Cure for about a day while in display tank.
My tank parameters are 0 ppm ammonia and nitrite, 5 ppm nitrate, pH 6.8, temp 76°F, Aquaclear filter and airstone, sand substrate, driftwood and wood stone.
I lost two Corys the second day after I added them to my quarantine tank. I did carefully acclimate them and they didn't seem stressed afterwards. I don't normally add medication to the tank unless I notice a problem. The second morning one of the Corys had severe pop eye in both eyes. Eyes were not cloudy but were severely swollen, one eye had actually ruptured. A second Cory had mild pop eye in both eyes and a third was on its side breathing rapidly (no pop eye). The Cory with the severe pop eye died that morning as did the one on its side with respiratory issues. I did a small 15% water change (parameters were normal) and dosed the tank with Kanaplex. I did a full three dose course of Kanaplex, then 48 hours after the last dose did another water change (25%) and have basically just been observing for further symptoms. The Cory with the mild case of pop eye recovered completely and up until today everyone has been eating and acting normal. I did have one that was away from the group quite a bit and not as active but still coming out to eat.
This evening when I got home, one of my Corys (I believe the less robust Cory) was basically floating near the surface; still alive, he will swim a bit when nudged, but not looking well. No sign of hemorrhage under skin, body normal with good slime coat, fins and barbels normal, respiration normal but extremely lethargic and just floating at surface. Upon inspection he looks perfectly normal. The remaining 4 Corys are eating and acting normal.
I do have Metroplex on hand as well as General Cure. Do you think I should try adding Metroplex to the water column or food? I do a water change every 5 days (tomorrow is 5th day) but even though I match pH and hardness and temp, I'm afraid a water change will push the sick Cory over the edge. Although the antibiotic appeared to resolve the original problem, I don't want to repeatedly dose the tank. I'm wondering if there could be an underlying parasitic problem (gill fluke?). None of the Corys look emaciated and even the sickly one has a normally rounded belly. Any suggestions?
Thanks crew!
Sue
<Hello Sue. One possibility is your Corydoras have been struck by something called 'Red Blotch Disease', likely similar to your standard issue Aeromonas and Pseudomonas infections that cause Finrot. It seems to be related to the stress caused by shortcomings in the environment, so rather than catchy per se, it's something several catfish might exhibit because they've all been stressed. When Red Blotch Disease was first described, it was usually associated with imported catfish that had been shipped in less that perfect conditions or held in overstocked tanks. Today you're most likely to see farmed or tank-bred Corydoras, but it's still possible for catfish to be kept in ways that cause them stress. Now, while the problem is bacterial, if the underlying triggering factors in the environment aren't fixed, antibiotics won't help. So while something like Tetracycline or Minocycline should help, let's recap the fundamentals. Almost all Corydoras prefer cooler water with plenty of oxygen -- exceptions including Corydoras sterbai and the Brochis species -- but certainly your common species like Bronze, Peppered, Panda, and Leopard Corydoras will all be best kept between 22-25 C/72-77 F. Another key thing is that the substrate should be both clean and soft. What I mean here is that the surface should be regularly siphoned to remove organic muck, with the top 1 cm or so being stirred beforehand to remove anything buried inside it. The substrate should be soft sand, smooth silica sand being ideal. Sharp sand and coarse gravel abrade catfish as they try to dig, making Red Blotch Disease more probable. One sign the substrate is 'wrong' is to look at the whiskers -- if they're short and rounded, then the gravel or sand is too sharp or too dirty. Since your catfish are newly bought, the problems might have been in the retailer's tank. That being the case, a clean tank plus suitable antibiotic should fix things if that's possible. I wouldn't randomly treat for flukes, worms or some other type of parasite because the symptoms sound so generic that an opportunistic bacterial infection strikes me as more likely. Cheers, Neale.>
Re: Undecided about how to treat further      10/21/18
Thanks Neale.
<You're welcome.>
I did lose the one Cory who was hanging out at the surface. Barbels and fins look good on remaining Corys.
<A good sign.>
The survivors are eating and acting normal.
<Likewise.>
I'm doing small water changes every few days.
<Wise.>
My substrate is sand and temp is around 76°F.
<Might lower the temperature a bit, certainly if these are Peppered Corydoras or one of the other cooler clime species. 22-24 C/72-75 F is probably optimal for most Corydoras, even if they tolerate water that's a little warmer. Certainly, adding extra oxygen can help, especially if your specimens are making frequent dashes to the surface for air -- a good sign the catfish are either heat-stressed or the bottom layer of water is oxygen poor.>
I think I have good surface agitation with AquaClear HOB and additional air stone.
<Good.>
You observation that it's stress related is the most likely cause of my losses. The LFS transfers them directly from shipping box to display tank and I found out that I had picked them up the same day that they came in. Poor fish!
<Ah, yes, this sounds like a bad situation.>
The remaining 4 (I lost three) are looking good and eating. I'll continue to keep their environment clean and stress free and keep my fingers crossed.
<Most Corydoras species are reasonably hardy, and some, like Peppered and Bronze Corydoras, a fair degree tougher than that. Good conditions, and perhaps suitable antibiotics, should help, given time enough for the fish to feed up and put on weight. Good luck! Neale.>

Corys       6/3/18 Hi there, Wondered if you could help, one of my corys has developed a large cyst on its eye. It’s completely over the eye. <Yowsers! That's quite the blister or cyst. Could be either, really. These are hard to treat satisfactorily, and prevention is really the thing to focus on. Corydoras are burrowing fish, and gravel isn't ideal. It tends to abrade their skins, allowing bacterial infections. The commonest symptom of this is the absence of whiskers, which on an adult Corydoras should be several mm long and distinctly narrow and tapering at the ends. Yours very obviously has abraded whiskers, which strongly suggests the wrong environment in terms of substrate. Of course sometimes Corydoras seem to do just fine in tanks with gravel, so there does seem to be a second factor at work, likely a generally unclean substrate that fosters the wrong sort of bacterial growth. Hard to say really, but I'd encourage you to look at your tank, especially the substrate, and draw your own conclusions.> Other than the obvious, the fish is not acting any differently. Any advice? <Treating cysts and blisters is difficult. Cysts tend to be solid, whereas blisters are (as their name implies) hollow with a tissue fluid centre, so may flop about a bit when the fish moves. Antibiotics can help with blisters, but cysts do tend to be viral, and there's really nothing you can do beyond waiting for the fish to get better itself. In either case, it's really about fixing the aquarium more than anything else, because there's no one parasite or pathogen involved, and therefore no "easy" solution you can buy from the pet store.> Thank you in advance! <You're welcome, Neale.>

Hopefully final update on Blobby White Panda Corydoras     11/30/17
Hi Crew, back in October I wrote to you about some sick Corydoras I had in quarantine that had developed a white coating and we had a bit of to and fro on different treatments, whether to euthanise etc. Despite trying every treatment available to me I have slowly lost more and more of the Corydoras including one that didn't have any of the white patches, but whose mouth seemed to have become swollen shut by small warty or tumorous bumps.
Tonight I finally lost the last of the white bumped corys.
<Sorry to hear this.>
I still have 3 Panda Corydoras that are mostly clear, one has a white lesion on his tail which hasn't changed for weeks, the others look a bit odd around the nostrils or on their fins but seem fairly healthy.
<Understood. Would continue to keep these isolated for now.>
The 2 sterbai Corydoras that were in the same quarantine tank never showed any sign of this illness, and neither have the rasboras that are also quarantined in this tank.
<Odd, but I suppose a silver lining.>
To recap: samples I have tried to take of this white matter have resulted in scraping off a waxy substance with no details of note when viewed under the microscope.
<May simply be mucous and/or decomposing tissue, neither of which will show much under the light microscope at low powers.>
Affected fish look really terrible but have mostly had an active demeanour, eating and swimming fairly normally right up until the day they die.
With this last fish I caught him in his death throes (laying on his side and struggling to swim or orient) and decided to euthanise him since his condition was so poor and I did not expect him to get better. After netting him out he appeared to have a red lump, an abscess or tumor I guess, on his caudal peduncle which looked to have broken to the surface and might be what finally did him in.
<Agreed.>
Since, unlike the others, he had very thick bumps with strips of healthy skin in between, I became determined to try and get a good sample off him to have one last look under the microscope. Upon closer examination I saw two tiny blisters on his white bumps, which finally clued me in that these bumps are not ON the skin, they are IN the skin. Or, rather, maybe they are the skin, thickened?
<Could be either really, and without seeing the fish, impossible for me to say. The fact is that many skin infections do cause blisters just below the surface, e.g., Whitespot cysts. So in and of itself, the fact there's a thin layer of skin over a growth or cyst doesn't rule out external parasites or infections.>
The stickiness I experienced when trying to take previous samples would have just been slime coat. I tried to scrape the thickest white patch and it was much like when your hands are wet for too long and the thickest parts swell and become easily damaged.
<Understood.>
With this new information I Googled once more and almost immediately came across a page about Carp Pox (Cyprinid Herpesvirus)
https://www.koi-pond-guide.com/carp-pox.html and the picture on this site looks pretty close to the blobby lumps that
were covering my Corydoras. The description of waxy lesions and fish that remain active and with a good appetite also matched what I experienced with my fish. I don't know if corys are susceptible to this particular virus but it does seem they had something similar all along which would explain why none of the treatments I tried worked. The page lists Lymphocystis and epitheliocystis as other possibilities but none of the pictures I saw of those looked anything like what was on my corys (and I suspect the antibiotics would have treated one of those).
<Viral infections are very difficult to diagnose except perhaps in those cases, like Carp Pox, that the symptoms are well defined and familiar enough that aquarists can recognise them easily enough.>
Have you heard of Corydoras being affected by a fish herpesvirus before?
<No; it's generally regarded as quite species specific, affecting Koi, its Common Carp ancestor, Goldfish, and its closely relative the Crucian Carp.>
I do remember our government in Australia talking about releasing CHV-3 into our waterways to kill pest carp species which makes me think they are sure it doesn't cross to other species.
<Indeed; what experimental evidence I could find on this suggests that native catfish, eels, and Rainbowfish, among others, were all unaffected by the virus.>
Mistakes have been made before though - cane toads spring to mind. I can't find much more information out myself but I feel that I have finally got a satisfactory idea of what was going on. I have been pretty strict with not sharing equipment between this tank and my other tanks and now I'm wondering if the usual net-disinfectant etc and washing my hands, will be enough to prevent the spread of this virus. Any advice on this front would be appreciated!
<CSIRO feel that the virus is not going to risk Australian native fish, though that's primarily because there are no native cyprinids in Australia, so even if the virus adapted a little bit, there are simply no even halfway related carp-like fish in Australia it could mutate towards. Catfish are far too distantly related for this risk to be significant. It's a bit like how humans can get mutated versions of viruses that originally infect monkeys or apes, but generally don't get viruses that infect cats or horses.>
Anyway just thought I would pass on my findings and my suspicions that this case was some kind of viral skin infection. Perhaps in healthier or hardier fish it even may not have been fatal as it took 8 and 9 weeks to kill four
of my Corydoras. So for now I will continue to monitor this tank and keep everything isolated as before and I will continue with just clean water and good diet as the treatment.
<Indeed. Just because CHV isn't the issue here, doesn't mean a virus of some kind can't be in play. There absolutely are viruses that affect widely disparate species out there -- the DGIV virus that affects Dwarf Gouramis has also been detected in certain other species. How common this is, and how dangerous, is hard to say. One issue is that there really are so many viruses out there -- and as aquarists we can diagnose so few of them -- there almost certainly is a Corydoras virus out and about, we just don't recognise it.>
Thanks for your help!
Bronwen
<Welcome. I'd tend to put down your experiences to bad luck. Might be a virus, might not. Hard to know. I'd isolate the sickly ones for another couple weeks at least, but if the disease has otherwise 'run its course' it may have run out of species it can infect. The Rasboras can probably go into the display tank, and the Corydoras sterbai may as well, since they seem to be immune or at least not affected by the virus, bacteria or pathogen. Good luck! Neale.>

Peppered Cory Illness      7/1/16 <Am responding here for timeliness-sake, but asking Neale Monks to respond as well> Hello, I have been assisted by your staff in the past for some issues with angelfish, so I thought I might get some help with my Corys. I have the following setup: 55 Gallon Artificial Plants Driftwood Sand substrate Fluval 305 Canister Filter 5 Corys (3 Peppered and 2 Green) 5 Neon Tetras 5 BN Plecos 4 Silver Dollars 1 Male Betta Food: Crisps, algae wafers (veggie and protein) daily. Betta gets a small amount of "Betta Food Pellets". Weekly offerings are bloodworms and/or Tubifex worms. Plecos LOVE cucumbers and the silver dollars enjoy romaine lettuce leaves. I do 50% water changes every week and clean my canister filter every 2 weeks (suggested is once a month but I do tend to overfeed with the silver dollars). Two of my peppered Corys are ill. Both have turned a dark, almost, black. Listless, no eating. <Mmm; something environmental at play here... introduction of a pollutant? With the lettuce perhaps... I take it the insect larva and worms you're feeding are processed... Not live> The larger of the two (female) is at least 3" long and she's just over 6 years old. The smaller (male) is about a year old and he is the same. The female has ragged fins and the male has a "scrape" on one side of the his tail where the paler "flesh" is showing and for a day or two had a red ring around the lower half of his eye orbit. <Physical trauma? From... the Dollars? The Plecos?> That has disappeared. The only outward sign of illness I have noticed is the female had an episode of her chronic swim bladder disease. From time to time (every 6-8 months), she will float to the water's surface and end up laying on her side for part of the day. I always withhold food and within 8 hours, she's great again. This happened last week. I was unable to do my regular weekly water change last Saturday, because I had the flu. So, my parameters are as follows: pH 7.5 Nitrate: 5 Nitrite: 0 Ammonia: 0 <Water temp.?> The female is my favorite fish. She's typically happy and LOVES water changes. She is just listless and I think she may have a little spot on her forehead, but I really can't tell with the dark color. I would sincerely appreciate any advice you can offer. All the other fish in the tank are happy and acting normally. I do notice some dark-looking (dark brown) algae or slime just beginning to form on my plastic plants, but this is something that I get regularly and clean each week..... Thanks! PS - Going to attempt to get a couple of pics to send as well <Good> Kristi A. Jones <Bob Fenner> Peppered Cory Illness /Neale      7/1/16 Hello, I have been assisted by your staff in the past for some issues with angelfish, so I thought I might get some help with my Corys. I have the following setup: 55 Gallon Artificial Plants Driftwood Sand substrate Fluval 305 Canister Filter 5 Corys (3 Peppered and 2 Green) 5 Neon Tetras 5 BN Plecos 4 Silver Dollars 1 Male Betta Food: Crisps, algae wafers (veggie and protein) daily. Betta gets a small amount of "Betta Food Pellets". Weekly offerings are bloodworms and/or Tubifex worms. Plecos LOVE cucumbers and the silver dollars enjoy romaine lettuce leaves. I do 50% water changes every week and clean my canister filter every 2 weeks (suggested is once a month but I do tend to overfeed with the silver dollars). Two of my peppered Corys are ill. Both have turned a dark, almost, black. Listless, no eating. The larger of the two (female) is at least 3" long and she's just over 6 years old. The smaller (male) is about a year old and he is the same. The female has ragged fins and the male has a "scrape" on one side of the his tail where the paler "flesh" is showing and for a day or two had a red ring around the lower half of his eye orbit. That has disappeared. The only outward sign of illness I have noticed is the female had an episode of her chronic swim bladder disease. From time to time (every 6-8 months), she will float to the water's surface and end up laying on her side for part of the day. I always withhold food and within 8 hours, she's great again. This happened last week. I was unable to do my regular weekly water change last Saturday, because I had the flu. So, my parameters are as follows: pH 7.5 Nitrate: 5 Nitrite: 0 Ammonia: 0 The female is my favorite fish. She's typically happy and LOVES water changes. She is just listless and I think she may have a little spot on her forehead, but I really can't tell with the dark color. I would sincerely appreciate any advice you can offer. All the other fish in the tank are happy and acting normally. I do notice some dark-looking (dark brown) algae or slime just beginning to form on my plastic plants, but this is something that I get regularly and clean each week..... Thanks! PS - Going to attempt to get a couple of pics to send as well <<Would start by reviewing the environment, as Bob suggests. Corydoras paleatus is a low-end tropical species that can be stressed by overly warm conditions; 22 C/72 F is ideal, and if you're keeping other tropicals that like cooler water (such as Danios, Neons, Swordtails and Platies) then doing a good-sized water change with cooler water can pep the fish up. If cooling the tank isn't an option, add an airstone and/or another filter, because lack of oxygen rather than raw temperature is the thing that stresses them. Ditto more frequent water changes just to improve conditions generally. Now, reddish or whitish flecks on the fins and between the armour plates (scutes) is usually a sign of bacterial infection. Early on, the sorts of antibiotics used for Finrot can work nicely. There's something called Corydoras "Red Blotch" Disease that does plague these fish from time to time. It's probably triggered by an environmental shortcoming of some sort. I've written about the disease over at Fish Channel, here: http://www.fishchannel.com/fish-health/disease-prevention/red-blotch-disease.aspx Take a read. Hope this helps, Neale.>> Re: Peppered Cory Illness      7/1/16 THANK YOU BOTH! I took some pics at lunch. They are attached. Perhaps temperature is an issue. I had been keeping the tank at 78-80 for angels that I previously kept (gave that up - no luck with that breed of fish), and I do recall my peppers doing much better with cool water at 72-74. <Yes> Oh, if it could be that simple.....please let me know what you think. I know my tetras and Plecos do great at lower temps....I believe the silver dollars will as well. <They should; yes> The pic of my female Cory on the red gravel substrate was within the first couple of months after I adopted her from my brother. I thought this would be helpful for comparison. THIS is what I'm used to seeing with her....and the changes may be subtle, but she's very special to me. The remainder of the pictures were taken today. The fish with the skinned up tail section (last two attachments) is the little male. The rest are of my female. The torn fins could be the result of the horrible advice I received 2 months ago from my LFS when they suggested tiger barbs would be good in this tank..... wow, were they wrong. <Oh yes; too nippy> I had those guys less than 5 days and they were ravenous, BUT I don't recall seeing any of this fin damage. When I compare the two pics of my female, her eyes may look a bit enlarged? She's always had such large ones.... <Both the before and current pix eyes are indeed too large> I will definitely do a 50% water change tonight and slowly lower the temperature. <Good> I'm pretty careful with the lettuce and Cukes, but please let me know if there is a specific manner of cleaning these foods before adding to the tank. <Soak them in tap water over night before offering. DO test the soak water for nitrates... telling> I typically serve raw after about a 2 minute thorough rinse under lukewarm water. <Again; the soak> THANKS again, you folks are SO knowledgeable and it is extremely reassuring to have a source of experience to go to in these times of illness with our little finned friends. <A pleasure to share; offer aid to other aquarists, humans who would better their understanding> Kristi A. Jones <BobF>

Re: Peppered Cory Illness /Neale       7/2/16 Thank you! Will follow all suggestions and let you know how they do....just two more questions: 1. Do you see evidence of an infection in the body condition of either fish? <You can't really tell this by looking at a photo. I'd assume so, and medicate as per bacterial infection. It won't do any harm, and will help if bacteria are at play here.> 2. Do you feel the large eye issue is PopEye or is there something I need to do to that end? <Pop-eye tends to fix itself when environmental issues improve, and assuming a secondary bacterial infection doesn't set in (again, another good reason to use anti-bacterial medications). Corydoras do get a bit "bug-eyed" when stressed, but usually recover from illness well, if the problem is caught early. Epsom Salt helps Pop-eye, so again, I'd do this alongside the antibiotics, as previously discussed.> Much appreciated! <Welcome. Neale.>