Well that varies from strain to strain and cycle to cycle. I believe the cycle changes every 7-10 day's for indoor growing.

Here is a good chart from GH to follow as a guide. They have a nutrient calculator on their website too. (when it works)
Zandor Reviewed by Zandor on . Zandor what additives do you use? I have probably read this somewhere, but for everyone's benefit would you mind listing your recipe GH 3 part, Rating: 5