I've used it in simple hydroponics (Kratky) for lettuce, spinach, etc., and as fertilizer for tomatoes, peppers, and cucumbers. The "standard" recipe for 5 gallons is 12 grams MB, 6 grams epsom salt, and 12 grams calcium nitrate. When I mix one gallon, I use a level half teaspoon of both MB and calcium nitrate and a level one quarter teaspoon of epsom salt. You're supposed to mix the MB first until dissolved, then the ES, then lastly the CN. The way I do it is when the plant is in bloom phase, I use a liquid CalMag solution, then MB. That way I'm not feeding it too much nitrogen.