Ahh right OK thanksi do it virtually every single grow with at least 1 plant off my res but just so you understand me i remove it completely off it and top feed the plant i don't leave it still sat in the autopot as if I'm top feeding you don't want it sat it the runoff . also regarding 500 or 700 i think it depends what meter you use and ec is universal that's why i use that but my meters have ppm and ec