I had since moved the reactor into the sump. It is still not working. NO3 of effluent is still red, same as the input, on both salifert and red sea test kits. Tried using AF Pro Bio S together with NP pro and it seems to make it worst. ORP moved to and stayed positive. Have now stopped dosing the AF solutions and left the reactor alone. Tried almost everything but can't bring NO3 down. Chaeto reactor, biopellet reactor, nitra guard bio cube, AF probiotic... Sent from Singapore Reef Club mobile app