Yeah, we know we would have to go with the ones that are not much bigger than 4 inches. And only about 3 in the whole tank. He wants colorful fish with a lot of personality. Ones that will interact with one another or greet us when we come home. Right now we only have a betta in his own tiny tank. Not even a half gallon. But he is so happy. We recently put up our 20 gallon tank. We want to add some fish to test the bacteria levels and things but are unsure when we can do that.