Quote:
Originally Posted by straightrazorguy
Another dumb question: why is "closed loop" better than the traditional return pump from the sump system?
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The other benefit that I *think* (I've never set one up before) they have is that powerheads like vortech's, tunze's, jaebo's etc. draw water in from all around the sides, then push it forward. On my tank, where my vortech's are sandwiched between an overflow and the glass this causes a wicked undercurrent where the water on the sand bed moves very rapidly in the opposite direction that the vortech's push. If you're trying to create a horizontal gyre where all the water moves either clockwise or counter-clockwise, you'll always be fighting the fact that water a few inches below and above the direction your powerhead pushes is going to be pulled in the opposite direction that you want the water in your tank to be moving.
With a closed loop, you'll still get some of back current as the water leaves the nozzle, but since the water being ejected from the nozzle is being siphoned from somewhere else, I think it would be way less severe of an effect.
Plus, you can hide the closed loop piping in rock work and it doesn't require you to have ugly powerhead glass acne that spends most of it's life in desperate need of cleaning.