Panda Corys Taking Chunks Out One Another?

[catxx]

So I have a relatively new 130L I've been working on the last 2 months. It currently houses 4 Panda Corys and 4 Kuhli Loaches. That's it. And lots of plants.

I just had a sit down in front of the tank to find one Panda missing almost all his tail, another with nibbles out of his and a third with a crescent moon bite-shape out of his dorsal fin. The forth, and the original Cory as I had 1 and added 3 more about 3-4 weeks ago, is unharmed. Has the original, largest, been asserting his authority? Has anyone else had this with their Corys?

The torn fins have no blood marks and no black ends, in fact the one with the loss of most of his tail looks like it's already regrowing.

 

[Harlequins]

I have never known corys to be aggressive that they would harm each other or anything else...

Are your loaches aggressive?

 

[catxx]

the Kuhlis are active, but I haven't seen them really taking much notice of the Corys! they have their mad moments.

the fact that my original largest Panda is unharmed with very full and happy looking fins has got me very suspicious!

 

[Inchworm]

Hi catxx

I'd be very surprised if it turned out to be C. pandas biting each other. I've never had a problem with kuhliis and corys either. I'd be much more inclined to think it was a case of finrot. If your tank is heavily planted, perhaps the bottom hasn't been adequately cleaned and uneaten food or other debris has accumulated there. Bacteria can easily grow in this.

Watch their barbels too, just to be on the safe side.

 

[catxx]

see I would think fin rot too, except there's no sign of those tell-tale black edges nor any blood spots, and the chunk out of that dorsal fin looks like someone nommed a hole out of it!

their barbels are long and healthy though.