On an sps dominant tank, how many times an hour are you turning over your water? I have heard 10 and I have heard 20. I run 2 3k cures and 2 mp40 for in tank flow on a 6 foot 165 gallon. I am looking yo upgrade from a mag drive to a dc return pump. I have 2-3/4 return lines plumbed to the tank with 2-1 inch drains.