I would start with 1/3 the recommended amount, and add an additional 1/3 every two weeks, while checking your N's and P's after each time period. Although not necessary, you could add a bacterial supplement, i.e. zeobak, NB7, biodigest, etc. to give it a jump start. Every system is going to be different, so I'd stick to the recommended amounts as a base line, until you find the amount that works best for you. In my case, I had a 180 predominant SPS mixed reef, with a 40 gal sump, so I calculated about 180 gal net after deducting for the rock and DSB. I found that 3 cups was about right for me, so slightly less than the recommeded amount. In my case I would use about half that amount over six months, at which time I'd remove and clean the reactor and replenish the pellets.