NaCl_H2O, your right, it is a sump capacity issue, but the water level in the tank is dependent on the pump flow rate, so a slower up will give less water displacement and will work with a smaller sump ( I guess at this point I want to keep the sump and would like to find a flow rate that will reach the equelibrium without overflowing the sump in case of power outage)
Tim, I got the pump from robert who was using it on his reef for 2 years with no porblems. It looks magneticly isolated like the other water pumps I use.