 The nutrient solution is oxygenated through air pumps or recirculation, and water is chilled to a temperature between 18-24C in order to maintain proper dissolved oxygen concentration, which is crucial to plant growth.Chilling the water also helps to prevent pathogens such as pythium, and delay bolting.PH (optimum 5.5-6.0) and EC (dependent on crop) are controlled with acid or base injectors and fertilizer injectors, respectively.