Bad over sight snowballs to big problem

[Jason McK]

I thought I was brilliant in my new tank set up. I have drilled the 2 returns in order to eliminate the need for Power heads. The returns are about 6 inch's from where the water surface is going to be.

The Big Problem is I have no means to break suction when the power is off. Is there a plumbing fitting that is like a one way valve? or do I need to start planing some big overhaul before I even get water into it.

Jason