Wasn't sure how to phrase that...but assuming I'm using either a wet/dry sump or a canister is there a height difference that I need to maintain, or is it OK as long as my filter water level is below my tank? Basically what I'm working with is maybe having the tank not that far off the floor, say 6", so the water level will be about 30" from the floor if it's a 2' tall tank...if I have my filter right on the floor will that be enough height difference?