we got alot in common, close to same size tank, housing an arowana and a moving bed filter. Are you going with K1? My arowana is close to 2 feet. It may be overkill but I have a spare room behind the tank so im running 3 55 gallon drums, first has 3 matala pads then #2 willm have 4 cubic feet of KI then to the pump/heater barrel which will be connected to my house drain to take care of my drip system