I got little Nova here following the unexpected demise of Dol. (I'm thinking something got into his water that shouldn't have :'( ) My logic was that Dol would want me to move on, to make another little fishie's life happier. I picked him based on two factors: his bright red coloring, and how attentively he followed (and follows!) my finger when I put it up to his jar. I didn't notice the little "split" in his tail till I got him into the tank. A small part of me thought it could be maybe leftovers from boredom-nipping, but that usually leaves the whole tail in tatters, not just a neat little chunk in the middle.