Dawn, or safer brand. Some soaps have chemicals that are not good for the plant. The best is to use Cocowet or equivalent. If you have no store that sells these I would recommend as plain as you can get dawn. Hope this helps. 1drop/gal
I'm going to have to disagree with Jawbrodt. Spraying your plants with an oil will burn leaves or at minimum cause stress when the lights are on. Its like applying suntan lotion to a baby and putting them in the sun all day.....Not a good idea. I mainly use Dynagro, but dip my clones before...