I've had a school of 6 bronze corydoras in my 3ft tank for about 3 months. 5 of them were added 3 months ago, and I've had no problems with 'em. But about two seconds ago, I walked into the study to see one acting a bit more 'dead' than typical corydoras. :( He's still alive, but I don't hold much hope for him.

He has a pink belly. That's the only outward sign of a problem, apart from his laboured swimming and breathing. Any ideas? :(
The rest seem fine... Hope it stays that way!

corys can survive in a tank with low oxygen, so they can swallow air from the surface and absorb it through their intestines, so I would suggest checking ammonia levels, redding may be just inflammation. is he the oldest one?

No, this is one of the young ones.
I tested the ammonia about one week ago and it was 0. There's no reason for there to be a mini-cycle right now. My test kit has run out so I can't test now. Otherwise I would've done so. If it is ammonia, though, wouldn't he have pink gills over a pink belly? Also, wouldn't the other youngins be affected?

Thanks for your reply. :up:

The labored breathing was what I was talking about for the ammonia levels. And the pinkish belly may just be inflamation. Inflamation can occur anywhere on a fishes body from what I know. Correct me if I am wrong but are you saying you don't make weekly water changes?

I do make weekly water changes. 20%. I just don't test water.

Wait a minute, I just caught a glimpse of pictures and if it has a pink belly it is probably just getting color to it since it is young like you said.

As for the breathing, I really think it has to do with your water.

He's gone now. :(
I'll get another ammonia test kit tomorrow. But the tank is fully cycled (running 4 years) and has had no reason to go into a mini-cycle.

The colour of his belly is especially pink, which is different to the other corydoras of the same age (presumably) in the same tank. It's not a natural degree of pink...

When I removed the dead one, his pink was more situated around where I'd imagine his ribs to be, not his belly as I previously said.

This morning, another one is displaying the same symptons, minus the pink belly. :(

Was his belly bloated or hollowed out looking? Have you changed any feeding habits?

do your have an air stone? if so, it may just need to be cleaned, they do clog up sometimes. also, has your temperarture changed recently? the tank may be too warm, or too cold. have you added anything new to the tank, and as catlover said, have you introduced a new food? are the fish that are labored in breathing, eating?

I've had two die now. One pink bellied, one not. There's another one acting unusually for a corydoras... Not sitting on the bottom, seeming 'lost'.

I just remembered that I added a young BN in here about a week ago. However, he is small and I have almost double recommended filtration on this tank (55 gallon, Fluval 3 and a Hydor 350).

The belly of the dead ones didn't look anything abnormal, except for the colour.
The feeding habits have not changed. Nor the food.
There's an bubble wall along the back. This tank was all freshly cleaned about 3 or 4 months ago, and the bubble wall was new at this time (along with the piping, etc).
Temperature's same old. This corydoras have experienced temperatures of 35C (they're set at 28C) before, over a heat wave we had a month ago or so.
Nothing new to the tank except for said bristlenose. That's bristlenose #2 in this tank, so they're used to have BNs around.
The fish that had the laboured breathing wasn't doing much except for breathing. :/ The one that is acting unusally now is not scavenging, either - just looking lost.

I've just done my weekly water change on the tank, today, by the way. (I saved a water sample for when I get a test kit.) When I did so, the 'lost' one was able to resist the current... He still seems strong, and he's not breathing heavily... But he's a little pink.

Other tank inhabitants: 2 sailfins, 3 black widow tetras, 3 white cloud minnows, 2 bristlenoses. 1 guppy who has got 'the droops'... As I call it. His spine has gone all saggy and he's having trouble staying near the surface. Most of my guppies seem to die this way, though.... I'm guessing it's what happens when they reach old age?

Thanks for your help, guys. I hope you can work out what's wrong and advise me what to do. I don't know what I've done wrong. :(

Hi Leema, can you see anything going on with the gills? Redness, inflamation, excess slime (do Cory's slime?)?

On a side note, here is an interesting fact sheet on Cory's.

http://www.scotcat.com/articles/article33.htm

I can't see anything unusual except for the pink belly. The gills seem mightly shiney, though I'm not sure if that was because I was looking at the fish so intensely and the light was just hitting it right.

I tested ammonia - none in the sample I took before water changing.

This has happened to me before... Cories just suddenly dying in a group. :(

The one that was looking lost has disappeared. :( I can't find him or his corpse. I turned up everything looking for him, but no luck.

The 3 I have left seem happy and healthy.

Any ideas? :(

None?

Very strange. How large are they and is there any chance you know how old they are or how long you have had them?

Have you added any salt? I'm just trying to get any more info that might trigger ideas.

They were less than an inch long... Probably 2cm or so. Had them for about 3 months, but I don't know how old they were. No salt, I know not to do that. :up:

If they were that small and you have had them for 3 months, how small were they when you got them.

I breed cories. and at 3 months mine are about 1 inch or more. So I would say that they weren't to healthy to begin with. Could possible have been stunted which would have shorten their lifespan considerably. Most of my cories reach full size by 6 to 8 months old.

Sorry Leema, This is totally off topic:
Susankat- Since you breed them, do you know what their actual average lifespan is? I love them to death! The kinds I keep are in my signature.

I'm out of ideas. I feel as though there are pieces of information missing, though I can't tell you what those might be. If they are having trouble breathing, then I would tend to focus on what's up with the gills. Any changes since you last post where 3 were left? What is the condition of the 3? Please be as detailed as you can. :)

The current 3 are fine! There is absolutely just acting like they are normal cories... Being hungry constantly, normal amount of that 'freezing' playing dead thing... Normal treatment of other fish (and treated normally by other fish)... I don't know what details to give because 'normal' is just the absolute description.

susankat - Wow! That's really interesting. These cories haven't grown at all in the time I've had them, despite being in a 55 gallon (understocked) tank. I've never had any cories grow in my care, and most of them have been from the same source (biggest & best aquarium store in my state). Do you think it's possible for them to be stunted and so unhealthy? If that's the case, I'd feel so much less of a bad fish mum. :(
If so - Any ideas on where I could get more cories from to make sure they're not stunted?
I was under the impression that corydoras are really slow growers, but obviously not the case. :o

Or... Is it something I'm feeding them? They get Wardley shrimp pellets, Flake Frenzy and Algae Wafers... A different diet needed?

Corys generally feed at the bottom of the tank and special sinking foods should be fed. These include sinking pellets like Tabi-Min and frozen blood- worms. Care should be taken to insure that all frozen foods are eaten quickly as they decay rapidly and can foul the tank. Don't overfeed!

They get fed sinking food and blood worms. The food doesn't last long with the corydoras and bristlenoses. There's never any left over.

Most cories will live at least 5 to 7 years depending on the type. The smaller cories like panda, and pygmies has the shortest life span.

How many times a week do you feed the cories bloodworms. If more than once a week, that could be your problem. Bloodworms should be used only as a treat as they can constipate a fish pretty badly, especially cories.

You should start giving your fish slightly cooked peas that has been shelled and mashed. It will help with these kind of problems. I give mine peas once a week so they don't get this problem. But then again I don't feed bloodworms so you may try giving it a couple of times a week.

I have a peppered cory that is growing like a weed! He was less than 1.5 inches when I bought him, and now he's pushing 3 inches! He eats a lot. "The rich mix" sinking tablets) I break them in half to make them easier to eat) hikari sinking foods (I also break these) occasionaly some algae thins, and anything that the tetras miss that hits the ground.

I feed them in the morning (they don't seem to know that they're supposed to be nocturnal) The cories love to play and chase each other across the back glass (I have a black background) sometimes they also play in the bubbles. They don't just stick to their own species, though they mix and play with other species, too. They usually do spent part of the day sleeping in along the back of the tank and in little caves.

They are fun little guys to have in the tank!

They probably get bloodworms about once or twice a month. But I can just stop. They haven't had bloodwroms for about 2 weeks.

A fourth one has died. :(

The two left are the eldest one (I bought fully grown) and another one of the 'bubby ones'... It was a bubby one that died.

Does it seem more likely that this group of fish I bought were stunted?

Starting to wonder if it was just a bad batch o cory's. Do you think it's possible they have been overbred at this point Leema?

I'm stumped on this one... unless it's dietary related.

FishyFry, I think you mean inbred. ;) One of the bubby cories did have a deformed spine, which may have been an indicator... Didn't realise when I got them.

SM, I've discussed what I've been feeding... Wardley Shrimp Pellets, Algae Wafers and HBH Flake Frenzy. Recently I've introduced HBH soft foods (shrimp and spirulina based). However, I introduced these foods before the first one died.

I'm trying to find a breeder of corydoras in South Australia. No luck so far... I might have to go interstate to get some.

un...inbred, yes. Thanks. :blink: Overly so? :)

Does somebody have a pic of these cory's ?

Do you want me to take a picture of the one left? :blink:

Have you got any empty tanks that you could try putting it in. Maybe there is something in that tank that they are not enjoying.

Nothing changed in the tank before the first one died, and they lived in it fine for 3 months (or whatever it was). Same water change schedule, tank already cycled, etc.

Maybe it's an internal parasite? I'm not quite sure what to advise at this point, it sounds like a Sudden Cory Death Syndrome or something like that. It might be a genetic problem, but if the older ones are dying now, I would suspect something contagious.

No, hakko. The eldest one is doing fine. The 4 that have died I got at the same time. There is two left - the old one and 'cory #5' that I got with the four that had already died.

What external signs would signal an internal parasite?

There are quit a few, Leema. Loss of appetite, belly swells up, feces trail, eyes starting to bulge, swimming weird, the list goes on. I agree with shelled peas on a weekly diet basis. Since I have started this with my fish, I have had no problems. Shelled peas act as a laxative. I don't know how it works, but I swear by it.

I think people are going to start saying that I think shelled peas is the answer to any fish problem! lol Funny thing is, Alot of times it is the most simple solution that we get results from. I have not lost any fish since I feed them one time a week a diet of shelled chopped to bite size peas. Make sure they are frozen peas and let them thaw out on the counter, do not boil them as they will lose alot of their nutrients.

Okay, I'll give peas a try then... :unsure: