Then use the sump for that reason and the fact it adds water mass to your system. plumb in the UV but do not use it unless you have MAJOR problems with crypt or other parasites/disease. It will kill off all the flora/fauna in the water column. I actually use UV in one of my reef systems but it is in a very specialized setup and the UV is designed around the water flow, sump, refugium and species in the tank. I am ALWAYS available to you or anyone with reef, aquarium, etc. questions.