I am using a mag 9.5 for my return pump with 1 HOB 600gph. I have used the head calculator on reefcentral and with the plumbing calculated in I am reducing the flow form about 700 to 575 is this going to cause pump problems? I could use flex tubing and not rigid pipe with 90's but won't look as good.

Hey Rawn, no it should not hurt the pump. I would plan on putting in a ball valve just as a back up incase you get more flow then you think. But if your calculations are correct, you should be fine.

I second Brandon on the ball valves. I have them on my return and intake just to be safe.