This is going to sound crazy but, common little feeder guppies. I bought a group of them for my convict to chase around and well, she can't catch 'em. They mated and I had to rescue a few of the fry and put in my community tank. I thought the zebra danios and harliquin rasboras would polish them off, but no. They grew up, and are breeding. They are really characters swimming free in a 72 gallon tank and fighting with the amano shrimps. The males have some of the prettiest finnage for not being the fancy variety. Can't see how you're supposed to "feed" them to anything. They can't be caught. I'm gonna have to start taking them down to the petstore and adding them back to their feeder population.