I'm using a Maxi Jet 1200 for a return pump on the two 20 gallon coral tanks. It creates a good current and handles the 3' or so of head just fine. It's running submersed in the lower tank though. The manufac claims the Maxi Jet will run externally, but I'm not sure I'd trust the seals on it for any amount of time. The Mag 3.5 should do a fine job as long as you use the manifold to split up the return as reefrunner suggested. One return would be too much current in one place. When I had my 10 going, I had about 300 gph
going through it via 3 MJ 400's (106 gph
) and everything did great.