These are in the family of Distichidus. The LARGEST Family of tetras. The affinis grow to a decent size so you can put them in your tank. The others in the family grow TOO large for a 60 gallon (24+ inches) Anyways, these are cool, because early in the morning they form a Large black-bluish spot on both sides of the body. Before I turn the lights on, I have watched these guys MATE!!! The only problem I found is that They LOVE to fin nip!!! Fin nipping usually stays in the group (I have 5) but once in a while I have seen bite marks in the tails of my albino tinfoils and once on my elephant nose. These guys need to be well fed to keep them from nipping!! here they are: