I have a 20H (sand bottom) aquarium with primarily tiny fish (Espie rasboras, Sparkling Gouramis, Pygmy Corys and a few dwarf shrimp). I currently have a HOB filter, but I want to upgrade to a canister filter. I can't decide between the Eheim Classic 150 and the Classic 250. Size-wise, the 150 seems appropriate, but I'm not sure if more filtration would be a better thing. Any help would be greatly appreciated.