I agree with everyone else...A wet/dry filter...one with a large sump. That way you can throw your heater in there and a couple of powerheads. This way, the water would be warm and well oxygenated when it returns back to the tank.
55 Gallon (2x Angelfish, 6x Clown loaches, 11x Harlequin Rasboras, 1x African Butterfly, 1x Otocinclus)
37 Gallon (12x Cardinal Tetras, 1x Gold Nugget Pl*co, 1x Goldline Tiger Pl*co, 1x Dwarf Gourami)
10 Gallon (Guppy breeder tank)
75 Gallon (EMPTY)
20 Gallon (EMPTY)