I have a new Marineland 90 gallon tank with a ProClear Aquatics 150 sump that I set up this week. It is drilled so that the sump is under the stand. The water level is barely above the bottom of the trim piece at the top. If I add more water, the sump starts to overfill. I have not turned the in sump skimmer on yet. Is there a way to adjust so that I can have more water in the tank without overflowing the sump? Also, what prevents the sump from overflowing if the power is off to the pump?