Tom Barr says that we should target 5 - 10 ppm as an optimum nitrate level. Is that 5 - 10 ppm NO3-N or 5 - 10 ppm NO3?? (My LaMotte test kit reads in NO3-N -- must multiply by 4.4 to obtain reading in NO3). Please help out a confused newbie lurker! Thanks, Jill