I found that the recommended GH nutes are too much for cannabis and also not appropriate for indoor growing. The 1,2,3 2,2,2 3,2,1, makes the plant too leafy and too tall during stretch for a short indoor grow space. The less grow, the better and no 2-2-2 cycle. I think 1-1-1 is good for early veg and then 0-1-2 is good for blooming. I do not have a meter but I kindof feel it out by looking at the water level, the color of the solution and the plants. When water level looks low, add full strength nutes for first week, then add half strength nutes for second week. Change every 12-14 days. I am just starting to get into the addivtives to see if they prove necessary. Sorry for rambling I am kindof baked-peace. Oh and keep temps low - that is the one thing I f'ed up on during my first grow.