When I was a kid I would catch small fish from the lake and keep them in a 10 gallon tank and over the course of a few years I had redbrest sunfish,shiners,yellow perch,crappie,and bullheads along with snails ,crayfishand little baby turtles in that tank at one point or another.But by far my favorite where rock bass,they kinda looked like little oscars with big red eyes and would eat any thing I put in there that would fit in their mouths.
Not sure how legal it is now to keep panfish that have no size limit in a fish tank.But even back then I knew it probably wasn't legal to keep under sized bass in a tank.But now that I see that you can buy them at a hatchery like ringneck did it makes me want to get a 50 gallon tank and get a couple!