I got almost same plumbing, except , on the end of the branch valves i got one more valve , same size like top one, like by pass, if i feed the tank No need to shut off the return pump, also keep water flow on reactors, in special the bio pellets, i got check valve to keep water level on swamp , protein skimmer air IN take extend the hose outside (fresh air) Bio pellets reactor ,return line tide to Protein Skimmer in take water , to export the bad staff. Bio pellets Reactor must run 24/7 never, shut off (in my opinion). (sorry , i see the check valve, lol)