bitten!

This morning I fed the fishes, then turned away from the tank to do water change on the QT. Went back to the main aquarium just a few minutes later and saw this:

I know that fish didn't have a chunk missing out of its tail earlier- I have been looking at them very closely each day for any signs of ich. My only guess is that Pinkie bit her.

He has often made threatening lunges at the other fish, but the gesture seemed half-hearted to me, just a warning I thought. Maybe he really was serious.

I have been mulling over what to do with the female barb in QT- if her tail starts to heal, I want to move her out of QT (must be stressful, being alone almost two weeks now) but have misgivings about putting her back in here so soon. She can't swim well now, I worry she won't be able to compete for food or keep away from Pinkie. I've thought of putting her in the smaller ten gallon, that one has a gentler current- but don't know how Oliver might react.

Now I wonder if I should put her back home, but take Pinkie out and put him in the QT. After a few days in solitary he might not be as aggressive to the other fish.

Incidental or not, this platy has been looking thinner than the others lately- belly not as round. I wondered if it was getting bullied away from the food, bottom of the pecking order. But noticed today that it keeps biting at the other platies- maybe feeling irritable from the injury?