reef rig or just sump

[demon666]

when i filled mine for the first time i filled the tank all the way up first.... including the overflow.... then filled the sump to where i figured the water levels would be..... then i turned on the return pump..... i had to keep adding water till the water levels evened out to where i wanted them as the pump filled the return pipeing and the remainder of the tank to get that perfect turn over........

[Ruth]

Well you learn something new every day. Reef Rig it is I prefer to have a refugium as well.
When I was trying to determine how full to have my sump/fuge I like to fill it so that the water is about 1/2 to 2/3 of the volume of the sump with everything running. Then I turn everything off - simulating a power failure to make sure that there is enough room for the back siphon of water without overflowing.