Depends on what you want. I wouldn't do mollies in a 10g. A 10 gallon is nice for a school of small fish. You could do some ember tetras, rasboras, or smaller danios like Celestial Pearl Danios. I have a 10 gallon with a school of 9 Danio Tinwini (was 10 one died a week ago) a blue cobalt goby...