Reactor question

I know I've seen the answer to my question in a post before but I can't seem to find it again. I'm a week into running new reactors, both are 150 phosbands from 2 little fishies, 1 for carbon and 1 for biopellets. I started them off at 1/2 the recommended dosage and I know I'm supposed to increase to full strength over time. But my question is what kind of time frame should I increase the dosage. Add the other half over a month? 6 months? Any help is greatly appreciated.