120 gallons! If that is right, 4.6 watts per gallon is a huge amount of light that will bring you a lot of grief. For that big a tank you don't really need anywhere near that much light to grow anything. You could cut the light in half and still do very well.thatguy2012;14473 said:wanted to try E I in my 120, and needed dosing amounts. 4.6 wpg 30ppm co2. i have purchased mono potassium phosphate(KH2PO4) potassium nitrate(KNO3), plantex csm+b from greg watson. I'm lost on the amounts of each.