Most nutrient concentrates have a built in buffering capacity to help maintain the pH level, however, there is a limit to how well this can be achieved in a soluble concentrate so pH ‘solutions’ are used to raise or lower the pH level. These are generally referred to as ‘pH up’ or ‘pH down’.

PHUP

The main active ingredient is usually potassium hydroxide (less commonly, calcium hydroxide). In soft water areas problems can be encountered when to much pH up is added as the extra potassium will hinder the plants uptake of magnesium and calcium

PH DOWN

The main active ingredient is usually phosphoric acid or sometimes nitric acid for use during the vegetative period. It should be noted note nitric acid is a much more aggressive liquid and should only be used in a diluted or mixed form. In hard water areas problems can be encountered when using too much pH down as the phosphoric acid will effect the plants uptake of phosphates.

SAFETY NOTE ON PH SOLUTIONS

PH solutions are aggressive active liquid chemicals and should be treated with extreme care.