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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.
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.
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.
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.
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.
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.
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.
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.
And they don't stay at the surface either, they dart up for a quick gulp and then right back down.
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.
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.>


Tropical fish to the USA - JCS. Shipping Corydoras        2/19/20
Hi. I am moving from the UK to the USA and want to take my albino Corys with me. I have been having hell finding a shipper, but did find one - who is concerned that they will be in the bags too long. (See their message, below.) They don't seem to be familiar with the Breathing Bags (Kordon)
that I was planning to use to ship the little guys.
<Have read the correspondence and am familiar with the Kordon bags>
I was planning on using the new Kordon bags, but then thought that, since the fish need to gulp air, there would still need to be an air pocket in the bag.
<Yes; I'd only fill the bags 20-25% full with water, the rest being gas>
So I was thinking about double-bagging them in the breather bags,
<Single; otherwise, not nearly breathable>
leaving a substantial air pocket to manage the air-gulping. They'd then be in a Styrofoam box (with air holes) in a larger cardboard box.
<Mmm; for thermal insulation, I would NOT poke holes in the Styro/s. The cardboard liner won't "breathe" much/at all anyway.>
It's my understanding that they absolutely should NOT have pure oxygen pumped into the bags, or they'll burn their gills when they gulp.
Unfortunately, they could end up being in their bags for 24 hours. I was planning on one bag per cory, so as to not overburden or stress them any more than will happen. Have you any advice for shipping albino Corys, or should they not be shipped long-distance? (The last thing I want to do is kill Big Bertha and the Boys.)
<Yes I do; and have worked in the wholesale parts of the trade. We (the trade) actually DO use oxygen on shipping Corydoras catfishes, at least 50% if not more, squeezing ambient air out and refilling with pure oxygen. The change of burning here is minimum via gulping. Callichthyid cats (and other facultative aerial respirating fish groups) mostly come to the surface to gulp air given low oxygen tension (concentration) in the water about them... and DO principally rest on the bottom when kept in the dark. They can stay in the bags (unopened) for a few days... 2,3 maybe 4, given they are "pooped out", i.e., NOT fed for a day or so before shipping, and the box kept about room temperature. DO label the cardboard as LIVE FISH and apply arrows with the statement, THIS END UP to discount leakage, breakage of the (more fragile) breathing bags. Bob Fenner>
Thanks for your help,
Mary Hudson
>> Hi Mary,
>> Many thanks for your enquiry.
>> We can only help with the transport of animals out of LHR or LGW so I have provided an email address below for an Agent who is in Scotland who may be able to help. Otherwise we would need to collect from Scotland, or the fish would need to travel from Scotland via LHR and this adds a lot of
time on them being oxygenated in their bags.
>> karen@petsonthemove.co.uk>>
>> Please let me know if I can help with anything else at all.
>> Subject: tropical fish to the USA - JCS
>>> Hi. We are locating to the USA this summer and have several small tropical fish that we would like to take with us. These are 10 albino Corys, about 3cm long each, and they can breath air in emergencies, and so they would ship in specialist "breather" bags with minimal water, packed safely inside an insulated box. They would need to be in a climate-controlled hold, though. (Similar to how the trade ships tropical
fish internationally.) They are exceptionally sturdy fish. but they really should not be in the bags for more than 24 - 48 hours.
>>> There are no prohibitions from the USDA, Customs, or Fish and Wildlife against bringing in pet tropical fish.
>>> We are moving from Glasgow and would be going to the East Coast of the USA. Our destination is not final at this time, but it is looking very much like it will be Binghamton, NY. .
>>> Are you able to transport pet tropical fish from Scotland to the USA?
If not, can you recommend anyone?
>>> Thanks. - Mary
Re: tropical fish to the USA - JCS       2/19/20

Bob - One more question for you. Any clue as to how to ship them? I have contacted several (like a dozen?) airlines and most don't allow them onboard as carry-on or baggage. I have to use their cargo services.
<Yeah; times were... if it was only one small bag, I might put it in my carry on luggage and if asked state that it was live fish and for "personal consumption" only; that is, not for sale, research... Nowayears air freight services is the route to go.>
Several of those have said I have to use a shipper service/agent.
<Mmm; I'd keep looking. Here in the USA you can find outfits that will ship domestically and internationally (where not restricted).>
I have contacted at least half-a-dozen such services and so far I'm not finding any that will ship tropical fish from the UK to the USA. How did you guys get your fish from all over the world shipped???? Thanks - Mary
<In the decades I was active in the trade we used a customs brokerage firm (Bill Flegenheimer in LA) and freight forwarders. BobF>
Re: tropical fish to the USA - JCS       2/19/20

Thank you for your help!
<Glad to be of assistance. Bob Fenner>


Corydoras Keep Dying      12/12/18
Good Morning!
Long time reader, first time writer. :)
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...>
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,
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.
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.>
<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.
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.>
<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, Sara L>


transporting Corys      6/28/16
Good morning WWM crew!
Thanks for your helpful website and advice.
<Welcome Steph!>
I'm plotting the introduction of some Cory Trilineatus to my tank and have come across information about their ability to secrete poison during stress. Apparently this can sometimes kill them during transport to their new home? I will only need to take them a short distance so they'll only be in the car for about 20 minutes, then of course the floating/acclimation
period. Do you have any suggestions for minimizing the chances of this sort of poisoning?
<Ah yes; the addition, blending of your system water in small amounts (a quarter or so of the shipping volume) every ten minutes or so; then discarding the mixed water, moving the cats (by hand if it were me/mine; to prevent tangling pectoral and dorsal fin spines in a/the net>
<Welcome. Bob Fenner>

albino Cory barbell loss, going for air                  ‏            11/9/14
Hi there,
My name is Gabby and I'm new to aquariums (had one since August) and loving it.i've slowly built a community tank (doing lots of research) since then and it's gone quite well.
I have a question about my albino Cory. I have a group of four and yesterday saw that the smallest one had lost his barbels. Today, I've seen him go up for air quite a bit, much more than the others. He's still quite
active, but during feeding seems to have eaten less than the others. Should I just keep monitoring him? Any suggestions?
<Catfish lose their barbels for two reasons. Or rather, there are two things going on that interact, resulting in the barbels getting shorter.
Keeping Corydoras catfish in tanks with gravel (especially sharp gravel) rather than sand causes the barbels to get damaged. Very fine (sometimes called "pea") gravel is better than regular aquarium gravel, but the best
substrate is silica sand (a lime-free sand, sometimes called "pool filter" or "smooth silver" sand). What happens is the barbels get damaged, and that's when the second part of the process, bacterial infection, sets in.
The bacteria cause the tissue of the barbel to die back, and over time the barbels get shorter and shorter. Improving filtration and water flow along the bottom level of the tank can help. Some filters (especially small
internal canisters and hang-on-the-back designs) often don't "suck" much water from the bottom and the outflow is very much directed along the top of the tank. This means the lower half of the tank suffers from low oxygen
levels, which causes catfish and loaches to swim up and gulp air. Note that under optimal conditions Corydoras rarely gulp air -- they're very much "facultative air-breathers" meaning they only breathe air when forced to do
so. That's unlike Bettas which are "obligate air-breathers" meaning they will suffocate if they can't breathe air because their gills are proportionally smaller than they should be (in the wild, Bettas live in places where the water doesn't hold much oxygen, so relying on their gills alone would be pointless). Anyway, under better conditions the barbels grow back very quickly, and on healthy Corydoras you'd be surprised how long they get, not far off half an inch!>
I also have a question about his lost barbells. When I decided on Corys, I decided on sand. The guy at the aquarium shop told me coral sand works, but now I'm wondering if it's the cause of his barbell loss.
<Coral Sand was a terrible choice. Bad advice from the retailer there!
Coral Sand is made of limestone. It's from the sea, basically mashed up seashells and corals. It makes the water hard and alkaline (i.e., raises the amount of minerals in the water as well as raising the pH). Over time, this stresses most freshwater fish. (Not all: livebearers and Rift Valley cichlids LOVE coral sand because it creates conditions they want. But Amazonian and Southeast Asian fish come from soft, acidic habitats and they aren't going to do well in tanks with lime-rich sands.>
The other three and their barbels are fine. Is this sand too rough?
<See above.>
Any thoughts or recommendations would be much appreciated. This little school is rivaling my Betta for favourite status, and I want to make sure they are healthy and happy.
<For sure a fun group of fish, the genus Corydoras.>
Thanks in advance,
<Most welcome, Neale.>
Re: albino Cory barbel loss, going for air                  ‏            11/9/14

Hi Neale,
Thank you for your quick response! I'll go out and look for silica sand right away.
<Cool. Aquarium shops sell it, but it's often cheaper at garden centres.
Just clean it well, or you'll make the tank really cloudy.>
What would you suggest to increase oxygen flow at the bottom of the tank? I have a hang off filter.
<If all else fails, an airstone weighted down so it draws water up from the bottom of the tank (that's what the air bubbles do) to the top of the tank.
Cheap and cheerful. Alternatively, there are all sorts of small pumps called powerheads that do the same thing electrically. Finally, you could buy a small internal canister filter and place it somewhere at the bottom of the tank, maybe hidden behind some rocks or plants, and let it push the water around.>
Man, so much to learn still!
<Part of the fun of the hobby is the learning. Corydoras are easy fish, and very reliable for beginners, but there are one two issues with them. Would direct you to this page:
Various links at the top that will take you to interesting/relevant articles. Cheers, Neale.>

Stocking question + catfish ID     8/29/12
Hey guys!
<And gals Rhiannon; how's it?>
I have a stocking question for you. I have a badly stocked 3ft (150litre) tank - I have 3 clown loaches, 4 angel fish, 6 rummy noses, 6 phantom glass fish, a Bristlenose Pleco and a black widow tetra. I'm looking to upgrade to a 6ft tank to remedy this. I'll move the loaches and at least 2 of the angels to the 6ft.
I came across an amazing deal on a 2nd hand 6ft tank (1830x460x600) on eBay with all the bells and whistles - but the issue is that it comes with fish and I was hoping for an unstocked tank so I could have free choice.
I asked for some clarification on the species in the tank. The owner doesn't know much about what type of fish they are so they sent me some photos and here's what I've worked out.
- 3 clown loaches
- 1 black ghost knife fish
- 1 Bala shark
- 2 gouramis (one female three spot, one female silver)
- Unspecified number Siamese algae eating fish
- 2 catfish (unknown species)
I'm pretty ignorant about catfish, so I've attached the photo of that one.
Would you guys be able to tell me what species that is?
<Mmm, yes. Is a Callichthys species, an armored cat of the same family as the popular Corydoras>
All the owner could tell me was that it was a catfish and a "monster" - apparently they have been growing very quickly.
<A peaceful animal as you'll find out>
I'm okay with some of the species (the loaches are great because I'd wanted to get at least two more to rectify the social issues going on with my three), iffy on others. I wanted to check with you guys - are there any serious alarm bells here? I get the impression that this tank may be fully stocked as is as most of these species get rather large -- is there any room for the new additions?
<Yes... the Bala may be skittish as a solo specimen... jump out over time... the Black Ghost Knife could get quite large here and possibly pick on its smaller tankmates... but there's room for more>
Thanks in advance,
<Welcome, Bob Fenner>

Seeking info about Callichthys  12/14/08 Hi there! I am back with yet another question, I hope it's not too much trouble. The LFS in my area is going out of business, unfortunately. They are sticking around for Christmas, and then they are calling it quits. Naturally, I was in there shopping for deals... In with their goldfish was what I initially thought was a porthole catfish, but after Googling around believe to be Callichthys callichthys. (It was simply labeled "armored catfish", which could mean anything!) It looks similar to the fish in the link below: http://badmanstropicalfish.com/stats/stats_catfish2h.html It was a dull olive green/grey color, so possibly a female? I believe this fish is also known by the common name Cascadura ("hard shell" in Spanish). Does anyone know anything about this fish, or know of a place to find more information? I can't seem to find much about them in my books, and the online information I have found has been spotty. Some websites say they get to 5" long while others say 8" or even 10" - and the acceptable tank size starts as low as 15 gallons, which I am certain can't be right. I have an unoccupied 29 gallon tank that I was going to turn into a brackish tank for guppies and platies, which might work out if this is indeed a brackish tolerant species. (We're only talking about 1.003-1.005 SG.) I imagine this catfish would keep the fry in check, which is fine by me! If I knew he would outgrow the tank, I could take my time finding him a more spacious home. Does this sound like an ill advised plan, or could it work? I never rescue fish from pet stores, because I know this only encourages them to restock. However, since the store is folding, I thought "just this once..." since I doubt anyone around here will appreciate a catfish like this. Thanks so much for any help! Happy holidays to you all, Nicole <Hi Nicole. The Porthole Catfish is typically Dianema longibarbis, a smallish (10 cm), midwater schooling catfish closely related to Corydoras. It's named after the row of roundish black blobs along the midline of the body, like portholes on a ship. It's a pretty good community tank catfish. Not a brackish water species, but otherwise adaptable. Now, Callichthys callichthys (the Cascarudo) is quite a different beast. It's quite a bit bigger (up to 20 cm) and unlike Dianema doesn't really swim about in midwater and prefers to slither about on the substrate between making mad dashes to the surface to gulp air. It's body is largely unmarked, but the pectoral fin spines have a distinctive orangey colour. It has tiny eyes! Callichthys callichthys is incredibly tough, and will tolerate slightly brackish conditions (around SG 1.003) without much bother. Hoplosternum littorale is a bit more of a brackish water specialist, and would be my recommendation for life with guppies and mollies. But there's not much difference between the two fish otherwise. Both species are boisterous, semi-aggressive at feeding time, but otherwise good community fish. Cheers, Neale.>
Re: Seeking info about Callichthys 12/14/08
Hi Neale, Thank you very much for your comments. I don't know why initially I thought it was Dianema longibarbis, definitely no "portholes" since the body was overall drab with no markings. I guess the barbels looked similar, and I only had a vague memory of what a porthole catfish looked like from a TFH article I read last year. I can't remember seeing any orange, so maybe it was Hoplosternum littorale instead of a Cascarudo? (Thank you for giving me the correct spelling, that improved my hits considerably!) I'll look more closely today... <Hoplosternum (and its sister genera Megalechis and Lepthoplosternum, both of which contain former Hoplosternum species) are generally quite easy to tell apart from Callichthys. If you look at the head of Callichthys species, you'll see that the eyes are very small. It also has a basically square tail fin. By contrast, Hoplosternum has normal sized eyes and a deeply-forked, V-shaped tail fin. Maintenance of all these species is very similar, except to say that Hoplosternum littorale at least favours hard water, and quite possibly brackish water, in the wild, and consequently does not do especially well in soft/acid conditions. By the way, the orange pectoral spines on Callichthys callichthys are only obvious on adults, and I believe just the males at that.> I guess I will go ahead and get the catfish, and plan on putting an ad in the online classifieds next year, to see if I can't secure him a more spacious home. Right now he/she is just under 4" or so. The only thing that troubles me is that everything I've read says these are schooling fish, to be kept in groups of five or so. Would a singleton be exceedingly unhappy? (He/she is already alone in the tank.) <Singletons of all these catfish (they're very closely related) do just fine on their own, provided they're not combined with anything overtly aggressive.> I could get some Brochis splendens, if that would help, and move away from the slightly salty concept and choose different fish altogether. <Brochis are superb catfish, and tolerant of a range of conditions, though again, I'd not put them forward as obvious candidates for a brackish water aquarium. Hoplosternum and Callichthys spp. catfish do occur in brackish water, so would make better choices. Hoplosternum littorale at least has a tolerance for up to 40% seawater salinity! Given it's closely related to Corydoras, it might be quite a surprise to many people that this species favours brackish water habitats in the wild.> As you can see, I am already feeling attached...I think it's the tiny eyes that I find so endearing! Maybe because of being very nearsighted myself. <Sounds very much like Callichthys! Yes, these are probably "legally blind" catfish, but they don't seem in the least put out by that. When settled in, they are goldfish-like in their pushy feeding time behaviour, and become very good pets. They used to be common in the trade, but from the 80s onwards much scarcer as people switched to smaller or more colourful tropical fish. Callichthys are hardy, do well at subtropical as well as tropical temperatures, and will eat just about anything, so are really very versatile fish.> Thanks so much, once again. Nicole
<Happy to help, Neale.>

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