[Myka]

So that's a manifold that will sit where or are those actually drilled in the glass? Is that a top down view or from the side? If that's top down you won't need two valves, just the one ball valve on the intake assuming the intakes are drilled on the bottom of the tank. Sorry, I'm not getting what's going on in your picture.

I personally am not a fan of manifolds. I figure you'd be better off drilling one intake, and 2 or 4 outlets using a 2 or 4 way OM. I like the water movement of that much better. Just my personal preference.