For my 75 I plan on running 2 canisters ( TBD ) connected to an internal overflow box running the length of the tank ( top rear ). The canister returns would go to spray bars either at the opposing ends of the bottom of the tank or across the bottom rear. Two questions. One, what do you think about the idea of putting a sponge ( like poret?? ) across the length of the overflow? And two, do you think the surface skimming and return configuration I plan will give me a good amount of movement? Tank will be heavily planted, looking to avoid excessive detritus build up.