I've been having my sump running for about 4 or 5 days now and it seem that in the return pump chamber. The water level is very low but when setting up the sump on the aquarium the sump was full and the aquarium display level was at a comfortable level. But, now the return pump chamber water level has drop to a point the pump is sucking in air. I did top off the tank with rod water and it's still doing it so anyone have any tips on this?