[canadawest]

I think that your idea looks great Steve.

Also consider one of those mechanized 180degree flow valves. (I forget what they are called)

You could put it where the 'Y' is on your return diagram. It would cause oscillating return to the two sides of your tank, thereby simulating more random water currents and tidal flow.

If my tank was drilled and plumbed, that's the route I would take.