i have a 20g sump for my 75g tank, i wanted a good turnover so i bought a return pump rated for 630gph! i also bought a Aqueon Proflex 110, 932 gph
overflow! Now i'm no math major but why can i only open the ball valve on my return line barely halfway before the return starts to empty! Is this just bogus advertising on the overflow box? It has a one inch bulkhead and a 1 1/4" hose straight to the sump! Backing off the pump made it sound like a freight train, so i swapped it with an "el cheapo" i have just for water changes! any ideas or advice would be greatly appreciated.