just use a ball valve to control tumble and use a good pump, i love my sicce pumps i own one of every size up to the 4 lol. do you have phosphate problems then run gfo, bio pellets dont take all phos out. if you give me a week or two, im getting a phos checker from hanna and im going to run tests on the bio pearls and take my gfo offline and see what they really do with phos.