Ooh okay, that helped understand the situation. Yes, the return pump flow is the only flow I have on my tank, so I think i will keep it pointing to the middle of the tank. Thanks a lot.This is more a personal preference, and also depends upon what other circulation pumps you have in the system.
If your like a lot of us, there are several other circulation pumps in use in the tank. In that case the flow from the return pump doesn't matter very much.
If it's just the return pump for flow then I'd want it pointing to the center or bottom of the tank.
There are also reasons for returning the water near the surface. The first is to break the surface of the water and give better gas exchange. This was dona a lot in the "olden days" when hang on the tank outsise filters were popular. With modern sumps and skimmers, this is not really needed, since there is plenty of gas exchange at other points in the filtration system.
The other reason is because returning the water at the surface prevents any back siphoning if power fails. As a note, I have yet to find a check valve of any type that I could depend upon to work when needed. A SW reef tank just gets too much stuff growing everywhere usually preventing a check valve from working when it's needed.