A lot of people here like aquaclears. On my 55 I have the emperor 400 and a penguin 200. I have to say the emperor is a great filter. I've never really had a problem with it at all and it flows a good amount for the price. Much better filter than the penguin 350. I only own one, and it is a 15 year old version of the ac50, the ac610. I don't have any gripes with it, it flows 200 gph and keeps my tank well circulated. But, if you were just to have one filter on the tank I would get the ac110 for the higher flow rate. Personally I would get 2 smaller filters, maybe 2 ac70s or a emperor 400 and another filter in the 150-200 gph area. Just try to get your total GPH over 500 and you should be fine.