I am going to use Mak4 pumps on my returns and closed loop. I was looking into the Ampmaster and even more so, into, Sequence pumps. They are both energy efficient, direct drive pumps, but as you guys mentioned, they have rubber seals. Unless changed on a regular basis, they will at some time, fail.
If your interested in Sequence pumps, contact Jayson at
www.saltwaterconnection.com
He uses them on his 500 gal. grow-out tanks.