How much flow do I need?

[jumeda33]

I have a 150 reef. I believe the two overflows handle 600 gph. I have heard that if the return pump is too big, it can cause mirco bubbles in the tank. I am in the process of redoing the sump with unders and overs to help get rid of those but should I go to a lower output return pump. I have two Tunze Turbelle pumps in the tank that really push some water. I want to have hard coral but the micro bubbles kill them. Right now I have a Rio 26HF that is doing 1350gph at 4 ft. and I have no control over the return pump speed. Any ideas?
Thanks,
David

[Bifferwine]

Is your system plumbed with PVC or vinyl tubing? If it is, it's super easy to put in an all-plastic ball valve to control the power of your return pump.

An alternative that I prefer is to plumb a T from the return pump, with one branch going to the display tank, and the second branch going back to the sump. The branch that goes back to the sump is plumbed with a ball valve, so you can control the flow to your tank by sending some of it back to the sump instead. I prefer this way because it puts less back-pressure on your pump, and simply redirects the water instead of blocking it.

[dustin_P74]

the reason that the return pump give you bubbles is because it is pumping out more water then it is getting cause the water level in the sump to drop, therefore letting air into the line. thats what the micro bubble come from, going with a lower gph pump will solve that problem

[jumeda33]

I have that clear tubing stuff. A little piece comes from the pump to a "T" thing and than a piece of clear tubing goes from each side of the T up to the bottom connection of each overflow. By the way, thanks for the super quick responses.
David

[daugherty]

check the line to see if it is sucking air were the lines are connected at.

[yote]

Another thing to check for.If the water level in the sump is low enough,the pump will cause little whirlpools that suck air into the pump.
If thats the case,just raise the water level in the sump.

[jumeda33]

I think I have enough water where the return pump is. You are right about the whirlpooling. Seems almost like no matter how much water I have there it still does that. I am also afraid to put too much water in case the power goes out. That is why I thought maybe a smaller pump in comination with the Tunzes I would still have enough flow in the tank but I don't know how to calculate what size pump. I think the guy that sold me the system was trying to create the proper amount of flow by using just the return pump. He never mentioned I should have other ways to create flow in the tank. I learned that later on.
Thanks,
David

[yote]

If you've got room,Try turning the pump over so that the intake is closer to the bottom.Thats what I had to do with mine when I was running a wet/dry.

[jumeda33]

never thought of that.