I have a 29 gal freshwater tank with a heavy bio-load. How much purigen is recommened for a 29gal tank?? The tank i think is still cycling but at the end of the cycle, I have about 15-20PPM of nitrate pH=6.5-7.0, NH3, NO2 all at 0. I am running a Fluval C3 for the main filter, a phosban 150 reactor for nitrate removal with 500ml of De-Nitrate and 100ml of Eheim Substrat Pro (for more bio filtration)and i put 250ml of Purigen in a Magnum 350 using it as a fluidized bed. Any other info that you need let me know, Thanks!!