I honestly have been growing for 3 yrs and I really never checked ppm except my first grow because I was so paranoid about everything after that I kinda stopped. I water them when the pots feel light, you can tell when its dry and when its not. I do make sure to ph my water between 6.6-6.8 though. I know that I should probably check my ppm once in awhile make sure there isnt salt build up but I mean I really havent had too many problems since I have been growing so I just stick with what methods seem to work best. I mean if I wanna make sure my plants are getting the right amount of ppm's I could do that and maximize my yields but like I said before I am happy with my results and never had any complaints about my buds. I do flush the last 2 weeks of flower but thats about it. The old growers adage is KISS (Keep It Simple Stoner!)