Why is my hydroponic nutrient solution pH dropping?

If you notice that your recirculating hydroponics nutrients pH is becoming more acidic (pH going down) and wondered why the pH is drifting then watch this! Using cilantro (coriander) growing in Grodan gro-wool under an Gavita Plasma LEP270 growlight, we demonstrate how fast growth can place huge demands on your hydroponic nutrients and how to adapt.