The pH is the most important factor for water culture gardeners to monitor because the pH of a nutrient solution reads the outcome of an electrical battle that is fought between the roots and everything surrounding them. When growing in pots, the run-off is the place to measure the pH level.
Why should the pH be monitored? The protein and enzyme molecules in a plant are structured in very specific shapes in order to catalyze a chemical reaction to build the plant cells. To do so, they need reactant molecules to fit precisely into their gaps like keys to locks; this means that all the negative and positive charges have to line up exactly. In fact, plants often change their own cellular pH to stop or speed up a certain enzyme reaction.
Three main things which change the pH that the plant feels are:

The pH of the water you start with
The growing medium (e.g. Rockwool is over pH 7.0, peat moss is – below pH 6.0, hardened expanded clay is pH 7.59)
The nutrient, since it can be mixed to form many combinations of elements that behave in different ways and which give up their elements to the plant at different pH levels. It is only after going through these three stages that a nutrient solution is able to readily give the plant the elements it favours.

We have a range of pH controls and pH testers to make sure that you are giving your plant the pH it needs.
EC in hydroponics
Nutrient solutions are generally made up by following label dose rates. However, label dose rates usually fail to take into consideration issues that could cause the nutrient solution’s concentration to be either too high, or too low. This is where an EC meter can be a useful dosing tool:
Setting the target EC:  When making nutrient solutions, EC meters are useful for setting the target EC. The EC requirement depends on factors such as the stage of plant growth and the type of medium. Burning of roots or foliage can occur if the EC is too high. If the EC is too low, deficiency symptoms can occur.