I think I got this right but let me get your opinion to build my confidence. I am going to put an overflow on my 29 gallon. I have found an overflow that is the tube type and says the capacity is 600gph. This will give me approx 20x turnover in my tank. Is this too much for my size tank. If so I think I can cut it down some with a ball valve right? Now for the pump coming out of the sump. I want my pump to not be able to pump back as much as the overflow can drain...right? So if I am overflowing say 400 gph and my pump can only pump 380gph I am ok right? As long as overflow is more than return everything will settle out? Thanks in advance for your replies.