<a href=showthread.php?s=&postid=7582595#post7582595 target=_blank>Originally posted</a> by psimitry
The only other way I can see to do it would be through a pressurized system - this one you could put below your tank. However, you would have to find a water tight bucket and then drill your bulkheads in the lid and make sure they're water tight as well. A powerhead would still be used but you'd have to have a pretty powerful one as you'd have to overcome gravity going out of the tank as well as gravity coming back up to the tank.
The powerhead would not have to be powerful, since you are pumping down and back up, the net affect due to the height rising back up would be equalized by the head of water going down--- think of a siphon loop... initiate a siphon with a long length of hose---- now raise one end back up so its almost level with your tank but the bottom of the loop still droops down to the floor... you will still get flow and without a pump and the water is rising up 4+ feet.
Now their is a hazard with running below your tank... the height of water in the tubing/hose going down and back up exert a slight pressure inside the bucket--- the pressure is not alot but the surface area of bucket lids presents a hydraulic problem... a small amount of pressure acting on a large enough surface area causes quite a bit of force.... see my post on this from several pages back...
http://reefcentral.com/forums/showthread.php?s=&postid=7441983#post7441983
Spuds...