This is correct and incorrect about the flow you can pump as much out flow as you would like without hindering plants fish or substrate. The bigger your out put is the slower the flow. I once had a 55 with a sump pushing 750 gph but my out take thingamabob was about 7 inches in diameter. That being said I never had a spot of algea once in that tank. My conclusion is organics in the water had no place to hide and a sump takes care of that 90% more effectively than any canister Or hob will ever push. But you end up with another problem the biomedia is so effective the tank can become nutrient deficient quickly if your not monitoring your dosing. Deficiencys also result in algea.Water volume turn over is related to the size/speed of a pump, not the volume of
a sump. Faster current/flow does seem to hinder algae developement. Fast flowing
streems seldom have any algae. And those aquascape tanks/w high lights in such
short tanks shows that rather well.
But you can only increase it so much before the fish, shrimp and if fast enough even the plants won't be able to tolorate it.
Reading some of the threads on the algae section and looking at those which talk/ask about having algae in one of those aquascape type tanks will also let you know that it
gets to be a rather delicate balancing act as well since they can't just crank up the current as much as they would like to.
Limiting the amount of light is a far better deterent to algae than current and much easier to control.