I use a Fluval 204 on my 20 gallon. Quiet as can be. I have no problems priming it, never have air problems or anything else. Would I buy one again? Yes. I have never used another brand of canister so I cannot compare them. Whatever you end up buying you should be happy. You can do a search of any of these forums and find good and bad experiences with Eheim, Rena and Fluval filters.