I have been running a 55gal fresh water tank with 1 large tiger Oscar, 1 blood parrot and a growing jack Dempsey. I am running a penn plax model 700 with grat results. now I just bought a 135 gal already established tank. it is running 3 over the back filters (im not sure what they are) I prefer external canister filter because of the lower noise level. Can you run multiple filters and what kind and size for this application?