Depending on several factors there is no way to tell for sure what the drain off will be to the sump if pumps go off but 2.5 Gals sound a little shy unless its a small tank like 25 gals or so ? As for depth for the pump ? it will seek its own level once you fill the tank to the overflows and then enough in the sump to get pump going. I'd set some sponge under the Mag power head to hold down vibreation sounds on the sumps bottom .. and I also put a MIP street 90 into the intake fitting of the Mag and have it looking somewhat downwards to pull right off ot the bottom few inches of the sump. _________ Some of the world's greatest feats were accomplished by people not smart enough to know they were impossible (Doug Larson) |