Pygmy sunfish would work. One of my personal favourites are log perch. Prickleback are cool and always beat everything to the hook when I’m creek fishing. Dace are really fun. I always wanted to try creek chubs but Canada’s native fish rules are very sketchy so I have refrained from keeping anything I catch. Creek chub would outgrow that tank (I have caught 10”+ chubs but some of the other chub species and stone rollers are cool and stay smaller (under 6 inches)