I was going to make a post about these actually. I prefer the name vampire tetra
I've seen them a few times then the other day I was enquiring about buying one in a store, and this crazy spanish guy was like "no no eez mai pet".
Then he say "watch thees watch thees" and picks up a random fish from another tank and plonks it in, and the vampire tetra hammered it, ripped it apart and swallowed it. Was fun to watch.
there tough to keep, If they settle in, there fine. Very tough to lean off live food. require alot of airation and ultra clean water. Get 4' in the wild