how much would you recommend for a system with 300-320 gallons total water volume? Am currently using the reef salt. Did 3 weeks of bio s. Currently using pro bio s and np pro. Plan on adding corals next week. All levels are good except nitrates which are still at about 20ppm. Plan on having a big bioload as far as fish. Skimmer is the reef octopus 5000 int. Thanks