I purchased a PF-800 overflow (got the larger one in case I upgrade my tank down the road). I am now trying to figure out which return pump I want. My tank will have roughly 4.5 to 5 feet of head, I would very much like to oversize this pump since I plan on upgrading my tank to 75+ Gallons maybe a year from now. I was looking at these pumps: Rio 3100 UL @ 782 gph - @ 5' approximately 450 gph Rio 2500 UL @ 900 gph - @ 5' approximately 580 gph I planned on splitting my return into two lines right before it returns into my tank. I would use loc-lines for this. This once again is for my 40 gallon display, however I plan on upgrading later a year from now.