By John Ragozzino

Maintaining balanced pH in hydroponic and aeroponic systems is extremely important to the yield, quality, health, and vitality of your cannabis plants. Nutrients will not be available for uptake by your plant if your pH is not regularly balanced. This causes nutrient deficiencies and can even kill your plants.


A figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline. The pH is equal to −log10c, where c is the hydrogen ion concentration in moles per liter

What the hell does that mean? Well, in layman’s terms pH is the measure of acidity or alkalinity of an aqueous solution. It is the potential hydrogen-hydroxyl ion content of the solution. Solutions ionise to positive (hydrogen) and negative ions (hydroxyl) bonds. When the solution has more positive ions in the solution it is acidic, and has a pH in between 1-6.9. When the solution has more negative ions in the solution it is said to be alkaline, and has a pH in the range of 7.1-14.

Why is pH Important to your hydroponic cannabis garden? Cannabis plants lose the ability to absorb some of the essential elements required for steady growth when pH levels are not properly maintained. This is more commonly known by marijuana growers as ‘nutrient uptake.’ There are many ways to increase nutrient uptake, but one of the easiest ways to do so is by maintaining the appropriate pH level for your growing application.

The ideal pH for most hydroponic gardening applications is between 5.8 and 6.2, except for Rockwool cultivation, which prefers a lower pH of about 5.5. In aeroponic applications keeping the pH as close to 5.8 as possible is crucial to your plant’s health.

Above pH 6.5 many nutrients and precipitate and stick to the walls of the hydroponic reservoir. Plants cannot feed on the nutrients unless they are dissolved in a solution; so when the nutrients precipitate out of the solution your plants cannot absorb them and nutrient deficiencies are sure to follow if the pH is not brought back into range quickly.

While a good digital pH meter is not cheap, they are far easier to use than pH measurement drops and color charts. Avoid the cheap knock off brands and make sure to read as many 3rd party reviews as possible when choosing which pH meter to buy. Maintaining digital pH meters is fairly simple in that the only thing you have to do is ensure that the sensor tip stays wet, but it is also an easy task to overlook when wrapping up your garden work. Be sure not to let your meter’s tip dry out because it causes damage to the sensor that can be permanent.

Most likely you will be using a digital pH meter, and one very important thing to remember is that many things can affect the pH of your nutrient solution including adding nutrients into your water, so always adjust the pH of your solution after you have added and stirred all of your nutrients into the water in your reservoir.