I run a bag of Maxspect Nano-tech Bio-spheres in my sump - Important to keep these clean, ideally these would be in my return pump chamber but i'm pushed for space - Any reason not to have them in a fluidised reactor fed from my return pump? I know they need to be kept packed tight to prevent wear from abrasion, but any reason for/against? I've googled but not found anyone else doing this.