In conventional soil gardening, the soil acts as a buffer for pH and is usually more stable than a hydroponic system. With hydroponic gardening, a fluctuation in pH can happen very rapidly and without warning. Because of this, monitoring pH continuously is always a good idea. If the pH fluctuates out of the desired range nutrient uptake will slow down or stop and the results could be disastrous.
The best way to combat pH change is to identify what is causing it. There are many reasons why a solution’s pH can fluctuate but usually it is one of three factors:
The water source is the heart and soul of any hydroponic system. A water’s pH is determined by the soluble chemicals it contains. The two most common chemicals affecting pH are CO2 and bicarbonate. Large amounts of free CO2 will cause a low pH and high amounts of bicarbonate will raise pH.
When we aerate water (air stones or recirculation), the chemical concentrations will change. Therefore, testing pH before aeration is useless. The stability of pH only occurs after CO2 escapes due to aeration.
The best solution to this problem is a holding tank for aerating water before it enters the hydrosystem or a reverse osmosis machine. Reverse osmosis machines are an essential investment for any large scale medical marijuana gardener because it ensures a quality water and a stable pH.
The nutrients we choose to use in our hydroponic systems directly influence our pH levels. High potency enzyme formulas can really bring pH levels down, while silicate or bicarbonate formulas can bring the pH up.
Start with a good base formula and stabilize pH before adding amendments. After adding each amendment check the pH again. This will tell you how much the given amendments are affecting pH and how you might adjust their concentration to adapt to your system.
A plant’s uptake of nutrients will effect pH levels as well. As a plant takes in nutrients the concentration of certain chemicals change in the water and adjustments may need to be made. Having a quality pH up and pH down in your nutrient cupboard is a must for any hydrogardener.
A colony of bacteria is one of the most common causes for pH fluctuation in hydroponic systems. If you have ever experienced a hydro-system that continually went acidic (pH goes down) you probably had a bacterial infection. If you are experiencing low pH ranges and after you make adjustments the pH quickly (within hours or one day) returns to a low state, you more than likely have a bacterial infection.
The best treatment for this is cleanliness. Remove any dead or dying root matter from your system. If possible, remove plants and flush the system with a diluted bleach or high concentration of H2O2. If plants cannot be removed, add a diluted H2O2 solution to the reservoir daily until the problem improves.