Know the nutritional requirements of your marijuana plants before you start. Know how strong the nutrients should be each week of your plant’s life, and know what the nutrients should consist of each week. Your marijuana plants need more Nitrogen at first, than switch to needing more Phosphorus to produce the buds.
Do not try to mix up your own plant food. Instead, start with a professional hydroponic nutrients product. These are usually three part systems and are complete (and easy to use). This is where you can choose to go organic with your nutrients which I highly recommend. Once your hydroponic gardening system is up and running and producing excellent results, than you can try mixing up your own special plant food if you like but make sure to take very good notes so you remember what works and does not work. Marijuana can be tricky because it grows so fast and it may take a few tries before you produce the sticky thc laden marijuana worthy of the doctors office.
Good luck and enjoy growing your own medicinal marijuana hydroponically today!