pH Meter – maintaining pH is crucial for proper nutrient absorption. For DWC your pH needs to remain between 5.5 and 6.5. I like to mix freshwater batches to pH 5.5 because the trend I have noticed is pH rises as plants absorb nutrients. You will need a pH meter to grow any hydroponic plants and it is recommended for soil grows as well.
EC/ppm Meter – An EC meter measures Electrical Conductivity to give you a rough measure of the nutrients in your solution. It is only a rough measure because pH up, pH down, minerals from your tap water and minerals the plants deposit into the water will all increase EC. You can get away with not using an EC meter but they make it much easier to top off your water rather than having to do complete water changes each time.
Baseline EC level – When using the chart above remember to subtract the baseline EC level. For example:
Tap water EC = 150
Measured EC = 1550
Actual EC = 1400
EC TO PPM Conversion: EC * 2 = PPM
