Back wen they wer babies, I had 4 reds. The biggest one ended up taking a chunk out of each of the others bellies and left permanent scars. I returned him to the lfs. Anyway that was a while ago and they have healed, but 2 of my reds lost their tiny ventral fins in the bite. U see a round semi-circle groove wer the fins were. So do they need those fins to live well? What are they used for?