Corydoras pygmaeus tail fins bitten off

[duckweed]

I have about 30 corydoras pygmaeus in my 3ft planted tank.
Yesterday I noticed a few of them swimming slowly/unsteadily and was shocked to discover that their tail fins appeared to be chomped off.

The other inhabitants of the tank include :-
- 1 corydoras sterbai (i think, its those normal spotted ones)
- 2 'helicopter' pleco
- ~50 boraras sp 'south thailand'
- ~100-200 cherry shrimps

There are plenty of hiding spots for the pygmaeus under bogwood.
Please advise which of the above fauna are likely suspects for biting off the fins or could there be any other reason (disease?)

Thanks all

[benny]

From your list, they don't seem to be likely aggressors.

How are the damaged caudal fins like? Torn and ragged? Or could it be a case of fin rot?

By the way, shrimps are know to have a go any anything they can get their tiny pincers on. Especially when the fishes are within reach when they are resting.

Cheers,

[stormhawk]

I reckon its the Boraras. Occasionally these little fellas can get nippy. The shrimps too are suspect. As long as the fins are not having any whitish edges, then there's no danger of fin rot. If fin rot is suspected, then you might have a problem with the pygmaeus.

[duckweed]

Hi guys,

I'm quite sure its not fin rot, here's a pic of one of the victims:


didn't know boraras are aggressive...

[Memnoch]

Ouch... that looks bad... sure you dont have a puffer or two lurking abts?

[Dragnet88]

i think should be pleco,
mine with gold fish and pleco same thing happen.

[stormhawk]

Wow, that looks nasty. But I feel its probably fin rot. Boraras are not known to attack their own tankmates. Nonetheless, to be safe, remove any pygmaeus with a damaged fin and transfer them to an isolation tank for now. Its a preventive measure, should the damaged areas be infected with bacteria.

[coryfav]

Looks like finrot to me too, and the tankmates look like a pretty peaceful lot.

[duckweed]

Thanks all for the advice.
How can I prevent fin rot?
Is it due to the water quality?
If so, how come its not affecting the other inhabitants?

Thanks again in advance