frayed tail on Mollie

[dizzykylie]

I recently got 2 mollies from an LFS. Both were supposedly female, although one was about twice the size of the other and much brighter. When I put them in my tank, my flame gourami went after the smaller one. After a few days he laid off and things cooled down, and the small one acted normally. Recently she has been hiding and I came home this weekend to find that her tail fin was split, making it look like it separated into 3 separate pieces. I've read about fin rot, and this doesn't seem to be that as there are no other symptoms. Could it be that maybe the other fish are picking on her again? COuld this be caused by agressive fish? She is no longer eating and is acting really weak, and I was just wondering if anyone has any idea what could be wrong.

Thanks.

 

[ROLLIN]

Yes the split fin could very well be from aggression. I notice a split dorsal fin or tail in my platy tank from time to time, but they heal quickly. Could you isolate the fish? What are your readings for ammonia, nitrite, and nitrate?