I had a biowheel 350 in my 20 gallon tank. upgrading them isn't that much more, and now I'm glad I did. I'm using it now in my 55 gallon. If I had got one that was just big enough, I wouldn't have been able to do that. I wouldn't go insane, but overfiltering, I think (unless you have fish who don't like strong currents, like bettas) isn't a bad idea.