welcome to the forum. heres my theory on fertilizing.. reading nitrates is ok, but the real question is, do the plants look good. if they are green, healthy, and growing then you're doing enough fertilizer. if they arent, then the nitrate readings give you a measure of where you are. if plants are not happy looking, and you have 5 nitrates, add a bit more fertilizer and get the number up a little, then watch the plants for a week or three, and adjust from there. the 1 pump per 10gal, 1x a week is a baseline average.