I am not 100% sure of the type and size of pump I want for my water fall project, but is there one which has a flow control built in. I am looking at about 12,000gph, but that might be too much based on the various methods of formulation I've seen. And that's another area of concern. I have no less than 3 different formulas for the required GPH, that range from 5,500 up to 20,000. All arived at from the same input data. Sure not an exact science is it.