i dont know of any such thing that exists, that average joe can buy. Theres ph meters, ppm (parts per million)meters idk if they have em for water, Brix scale meters. You start with good clean water, thats the right ph and aeroated with airstones, and then dose the right amount of nutrients, mix it, and then check/adjust the ph again. hydro shops or htgsupply.com have lots of different meters. thats all i know