PlanetCatfish.com

Been having problems with a cory and was suggested to try asking here.

1. Water parameters
a) Temperature range 75F
b) pH 7.8
c) GH 20
d) KH 10
e) Conductivity or TDS (if GH and KH aren't provided) 500TDS
f) Ammonia, Nitrate, Nitrite levels (Most LFS's will check your water and give a list of readings) 0 ammonia, 0 nitrate, 0 nitrite
g) Water change frequency every other day in the hospial tank. Whenever the nitrate rises in the 75g (it's pretty heavily planted)
h) "Routine" water treatments (e.g, chlorine/chloramine or ammonia neutralizers; pH or hardness adjustments, anti-stress chemicals, tank-cycling bacterial mixes). Prime water conditioner, flourish excel and some other plant ferts in its original tank

2. Tank set up
a) Size 75g
b) Substrate organic soil + black diamond blasting sand
c) Filtration SunSun 302
d) Furnishings
e) Other tank mates 5 more bronze corys, 7 harlequin rasboras, 2 peacock gudgeons, scads of snails (ramshorn, malyasian trumpet, pond).
f) How long has it been set-up? been set up since January 17th or so.
g) Food used and frequency Frozen bloodworms once or twice a week, Hikari sinking wafers 2 pieces split between the corys and the rasboras intent on stealing it.
h) Recent changes in the tank which occurred shortly before the disease/problem appeared (if any; e.g., changes in water source or water treatment, changes in decorations or substrate, replacement or changes of hardware (filters, heaters, etc.), and additions or removals of live plants or live fish) The sick one is from the first batch of 3 corys I added to the tank since the stores I went to didn't have enough to buy all 6 at once so the 6 fish were added in a two day span.

3. Symptoms / Problem description or history
I noticed a white bump on its fin around the 15th. It looks kind of like a droplet of white school glue. On the 17th, the cory was upside down on the substrate and I thought it was dead until it wiggled away when I went to scoop it out. It kept of going between righting itself and going on its side or belly-up until the 18th or 19th. The lump seems to have shrunk slightly. But currently it seems to be getting paler.

the 15th

the 17th

the 19th

the 21st


4. Action taken (if any)
Cory is currently in methylene blue treated water in a hospital tank

5. Medications used (if any) / changes in fish observed since treatment began (if any)
methylene blue. Lump has shrunken slightly, ability to stay upright regained. Paler than before.

All I can say is do not worry about it.....
My corys have had the same thing on and off for the last 3-4 years. None of them died, none of them have had any side effects because of it. None of my other fish caught anything at all.
It was suggested here to me it is because of too rich diet. I've starved them and it still didn't clear it. My corys were never fed on rich diet to start it. I've tried a range of meds over the years to try and "cure it" while I thought it's a disease. It isn't.

So stop worrying. It's unsightly but that's all. Your corys and the rest of your fish will be fine. It's not contagious. It seems that whatever it is, corydoras have it but it does not affect them at all otherwise in any way.

The lump is always at the base of the dorsal fin and looks like a "tear". It never appears anywhere else. Sometimes it shrinks and sort of looks ragged(not the fin but the lump) then it fills up again... In time it goes away... or stays for weeks and even months on end. The cory(s) will be just fine. Put them(it) back in the tank....

I noticed a white bump on its fin around the 15th. It looks kind of like a droplet of white school glue. On the 17th, the cory was upside down on the substrate and I thought it was dead until it wiggled away when I went to scoop it out.

Your cory is not "dying" because of the lump. It's for totally different reasons in my experience and my opinion. You should concentrate on water quality for a start.
Blasting sand sounds rough. And the cory seems to be missing its barbels (I could be wrong, it's could be the pictures). How long has the tank been setup for? Soil also releases ammonia at the start. Perhaps a mixture of unsuitable substrate and the consequences of it.

My opinion my sound harsh to you but I have had corys with the same issue for years and as corny as it may sound, they do not keel and die from this. Your cory is suffering for different reasons. I just hope you forward your attention in the right direction.

Also, I wouldn't keep any fish, especially what one may think is a sick fish, in a small plastic container in order to "cure" the fish....It's just common sense. Fish can only get better when they aren't stressed. Isolation in an unsuitable container is extreme stress for the fish. Extreme stress means very weak immune system that can't cope with what a healthy fish would. In other words....similar to the fish losing the will to live.....The only thing that remains is the experience that we humans acquire while experimenting with the poor things which is essentially the memory of "killing" fish. ......Talking from experience...

It's only in the tiny cup during water changes and because it's way easier to photograph it when it's got nowhere to hide The hospital tank is 5 gallons with a heater. I get that isolation isn't the greatest for a shoaling species, but if I'm not sure what it is, I can't tell how contagious it is so like what do you do about a sick (or possibly sick) fish without isolating?

The tank has been set-up since January 17th or so. It's been testing 0 ammonia for a while with the API liquid test kit which is reasonably accurate as far as I know. Didn't add fish until the nitrogen cycle got going using a mix of Seachem stability and filter media from a different tank.

I've seen people say black diamond sand is fine for cories and some people hate it. The fish still has barbels and so do the other 5 corys. But I will keep an eye on it.

Im having this same issue, the fish behave and eat fine.
When i quarantine and treat it with paraguard it disappears. When I put them back into the main tank it come overnight.
Seen this happen only to bronze/emerald corys.