4650 gph on a 315? Geeeez.
yea i was thinking its a little much too but ill hook the 2 pumps up anyways to find out. my sump is massive as well. 5x2x22 inches high. there will be a lot of media and 3 compartments that the water has to go through. itll add another 100 gallons or so of water so that makes the total 420 +/-. also the pump to the top of the tank is at 5 feet height. that lessens the GPH as well!!!