[marxsman]

Can someone please explain a closed loop vs. open loop?

And also is there a referance that shows and explains how to build the plumbing.

or EREEFIC, where did you get your design? it is absolutly fabulous. I would like a websight or a book that explains how to plumb everything. I am still doing the research for a 120 gal that I will set up soon.

[golfish]

A closed loop is just for flow...have you ever used a canister filter? just think of that as a closed loop with out the canister just a pump.

I don't know if this will help much but here's a few pictures of my closed loop. Water is drawn from the tank by the Reeflo pump (see bulkhead in middle back of tank. Water flow from the pump to the manifold where its distributed to two 1" Sea Swirls (each end of tank) and two 3/4" lines on the sides of the overflow.