IANKgrow

As long as your water has more than 150 ppm of dissolved solids, then calcium deficiency should not be a problem for you. If it has less than 150 ppm, then it’s probably a good idea to add some calcium and magnesium to make sure your plants will receive enough of these nutrients to thrive.

The pH level also comes into play with a calcium deficiency in a hydro setup. If the pH level is outside the range of 6.2 to 6.5, you are more likely to have a calcium deficiency than if it is within this range. Flush out your system with fresh water that has the proper pH level as well as a boost of nutrients to restore the balance.

In this case (RO) you will have to prepare the nutrient solution in a different way: before adding any other fertiliser, pour two parts of calcium per one of magnesium until reaching an EC value from 0.0 to 0.3-0.4.