hi I have a question about powerhead/pumps and routing water flow for a tank I had an in sump skimmer and a second powerhead to pump the water from sump to tank with at least some of it skimmed skimmer died power head died I wanted to up grade got a new skimmer but its in-line do I need two pumps one before skimer and one after or would one before skimmer work and allow the water to keep going up the hose to the tank?