if you use super natural brand you can throw your meters away its designed to run 700-1000ppm thats 1 to 2 teaspoons per gal and buffered so you will never need a meter...you only need a meter if your using crappy nutrients sorry about the dirt but thats the way it is or you can buy billions of dollars of garbage and make a recipie but lifes too short to use crappy nutrients:thumbsup: