The Streams can certainly be used as the only source of water movement; they move a lot of water in a very broad flow pattern with less velocity than standard power heads. The 6100 moves more than 3000 gph and I have seen them used in eight and ten foot tanks where the flow bounces off the other end of the tank. Personally I prefer the use of two pumps at either end of the tank and using the multicontroller to create the pulsing water movement. It seems far more natural than one pump blasting in one direction at the same speed. The pulsing that the controller creates reminds me of the water movement that I have felt while snorkeling or diving.