pH is a measurement of the acidity or alkalinity of a solution. On a scale of 1 – 14 neutrality is represented as 7. The ideal pH for almost all Hydroponic applications is 6. pH for RockWool cultivation should be slightly lower, ideally about 5.8.
Ionic nutrients are especially formulated to ensure that pH is close to 6 when made up with reasonably pure water. Unfortunately water quality varies dramatically from place to place.
You may find therefore that you need to make small adjustments to your nutrient tank from time to time. It is very important to check pH the first time you make Ionic solution. As long as your reading is within the acceptable range (5.8 – 6.3) you need make no adjustments to pH at this time. You should keep a regular check on pH at all times.