Since there is a known relationship between EC and TDS readings you only need a TDS meter.

There is a correct order to adding nutrients.

1. Take a small sample of your water and set it aside. Check your Ph and TDS so you know where you started.

2. Ph balance your water and let it stabilize.

3. Add your grow nutrients (if you are using a 3 part then itā??s Micro, grow, bloom in that order)

4. let it settle again and check your PPM and Ph. Re-balance the Ph again if you need it but you should not.

5. Now you have your PPM you can add your Cal-Mag Plus, your B-1 or what other nutrient supplement you are adding.

For example if you are using GH 3 part mix and you want to give them week 3 veg feeding 1000-1400 ppm, light 18/6. You balance the Ph first then add 6ml pr gallon of micro then 12ml pr gallon of grow then 3 ml per gallon bloom is added last. Stir in all the nutrients and let it settle for about 5 min so the Ph buffers can balance out. You donā??t want to play the Ph up and Ph down game you will only loose in the end.