pH is extremely important in hydroponics because it affects the availability of key nutrients that plants need to grow. The optimal pH range is between 5.5-6.5 for most plants. Staying within this range allows plants to properly uptake nutrients like nitrogen, phosphorus, calcium and magnesium through their roots.
I generally recommend aiming for a pH around 6.0 if you can. At this midpoint value, most nutrients are readily available. If the pH drifts lower, into the high-5s, micronutrients like iron, manganese, copper and zinc become too available and can accumulate to toxic levels. A low pH can also lockout calcium and magnesium availability. On the flip side, if your pH creeps higher, towards the low 6s, you increase the chance of phosphorus deficiencies and iron/manganese deficiencies.
Checking and adjusting your pH is crucial when mixing up a new batch of nutrient solution. It also requires periodic monitoring to account for pH drift. Most hydroponic systems benefit from checking pH at least once a week. Purchase an accurate digital pH meter and calibration fluids to properly monitor your levels.
Getting your pH dialed in usually requires adding pH Down (phosphoric/nitric acid blend) to lower the levels or pH Up (potassium hydroxide/sodium hydroxide) to raise the pH levels. Only make modest adjustments at a time and give the reservoir mixing time to reach equilibrium before testing and adjusting again. With routine monitoring to keep your pH locked in around 6.0, your plants will have access to all the essential nutrients they need through their roots.
