check the gh web site. Look for their nutrient calculator. It is spot on and I swear by it! DO as it says exactly. Just enter it in as it says and chanve to ml or ounces and hardwater or ro and expert or simple and agressive or normal by checking boxes and boom!. I was a skeptic but not now. I use the agressive growth. I use the three part hardwater with tapwater and hardwater micro and this is the best time ever. As long as I dont get lazy with the top offs! God i let the reservoirs get low sometimes. hehe.