Setting the Right pH for Your Hydroponic System

In any horticulture technique, maintaining the value of pH in a narrow range is of paramount importance. Hydroponic systems are no different. Many gardeners focus on water content, light, and nutrients- and forget to maintain the ideal pH range, rendering their plants vulnerable and weak. pH plays an important role in the healthy growth and development of the young plant. If the pH of the hydroponic system is too high or too low, plant enzymes won’t work properly, resulting in stunted growth of those beloved plants of yours. The optimum value of pH ensures the availability of important nutrients to the crop, while a volatile pH can result in withering and poor growth of plants. Although pH variations are normal in hydroponic systems, they can be managed easily with the right tricks up your sleeve.

What is pH value?

pH is simply the concentration of hydrogen ions in an aqueous solution. The value of pH determines the acidity of a medium. Ions are extremely tiny particles, and a small sample of any solution would have billions of ions. Therefore, we use a logarithmic scale for the measure of hydrogen ions, i.e., the pH scale. On the pH scale, a value greater than 7 means that the solution is basic, and a value below this threshold would mean that we are dealing with an acidic solution. Pure water has pH 7, which means that at this value, the number of hydrogen and hydroxyl ions are equal; the solution is neither basic nor acidic- it is termed neutral. This measure of acidity or basicity matters a lot to the plant; since it is the decisive factor that determines the availability of nutrients. Different nutrients are available to a plant at different levels of acidity. If you want your hydroponic plants to thrive, you’ll have to find the right balance between acidity and basicity- a value where all nutrients are available for uptake. This value typically falls in the acidic range.

Ph Scale

How to measure the value of pH in a hydroponic system

Measuring the value of pH in a system is simple and a straightforward process. Even if you didn’t pay attention to your high school chemistry teacher, this should be a piece of cake. Although there are many methods for measuring the pH value of a hydroponic system, we will take you through the easiest ones- those which are easy to use and involve the least chemistry mumbo-jumbo.

Litmus paper

Simple and effective- the litmus paper method is the easiest method to test the level of pH in any hydroponic system. The litmus paper is a paper strip covered in a pH-sensitive dye extracted from lichens that will change its colour when it is put in contact with the hydroponic nutrient solution. The resultant colour can then be matched with a corresponding colour on a pH chart. Although simple to use, this method has its drawbacks. This method is not very accurate and does not determine the pH correctly if the nutrient mixture is qualitatively inconsistent.

Digital pH meter

The most effective yet slightly expensive method of measuring the pH value is via a digital pH meter. This pH meter for hydroponics is pen-shaped and is extremely easy to use. Also known as a pH pen, this digital pH meter comes in various sizes. Simply put the electrode tip inside the solution, and you will see a pH value pop-up on the LCD screen in a minute. The problem with digital pH meters is that they often require manual calibration. If you are not a fan of calibrating these meters every time you use them- we suggest you get one with auto-calibration.

Az PH Pen

Liquid-based pH test

Using a liquid-based pH test is more accurate than using a paper strip test. It is a simple and inexpensive method to gauge the pH level of a hydroponic system. To conduct this test, take a small amount of nutrient tank solution in a vial, and add a sensitive dye to it. The colour of the nutrient solution in the vial will change, which can then be checked against a standard chart, where each colour represents a specific pH value.

What causes pH fluctuations in a hydroponic system

There are many factors that might contribute to fluctuations of pH in a hydroponic system. This will most likely occur if you have added an acidic or an alkaline nutrient to your system. Excessive acidity or basicity results in pH variability in the hydroponic system.

Another probable cause of pH fluctuation lies in the nutrient concentration. When the nutrient solution is less than 4 litres, then the solution becomes concentrated. Plants absorb water from the hydroponic nutrient solution, leaving behind nutrients that make the solution excessively acidic or basic.

If you do not clean the nutrient tank well, the organic growth of algae and bacteria can alter the pH levels as well. These organisms feed on the nutrients in a tank, releasing acidic gases in the process- ultimately lowering the pH value.

If you do not want any of these factors to affect the pH value of your hydroponic tank, then make sure to keep the tank full of nutrients, remove any harmful algae or bacteria, and test the pH tank often.

pH ranges for hydroponic crops

Different fruit and vegetable crops prefer a specific pH range. The general pH range for the majority of plants and vegetables is 5.5-6.0. Melons, apples, citrus fruits, and others thrive in very range. There are some fruits which prefer slightly acidic pH level as well, such as blueberries and raspberry.

At the same time, there are a variety of plants that can bloom in a wide range of pH. Pumpkins and tomatoes can even grow in pH ranging from 5.5-8!

Adjusting the value of pH in a hydroponic system

If you notice any fluctuation in the pH level, then it is important to bring it back within the normal range. There are many methods to do so. Here are the 4 most common methods that will allow you to maintain the pH value of your hydroponic system.


Use the right blend of chemicals

If you are an expert gardener, then you could use the right blend of chemicals to adjust the pH of your hydroponic system. Food grade citric acid is a good choice to make your hydroponic crops acidic. These acids are diluted and do not pose any threat to the plant’s health. Although there are other acids such as sulfuric acid and nitric acid as well, which are much more potent and can lower the pH far more quickly- we suggest you refrain from using them. These chemicals can damage the root structure of the plant and can be perilous for a young plant’s development. While using these acids, make sure that they do not come in contact with your hands or eyes. Otherwise, they could cause burns or rashes.

If you are aiming to increase the pH value of the hydroponic plant, then baking soda would come in handy. It is commonly available in every house and can easily increase the pH value without harming the plant’s development.

Although readily available and easy to use, these chemicals are occasionally ineffective or do not produce the desired effects. Therefore, we suggest you use other methods such as organic pH up & pH down adjusters or pH buffers.

pH up and pH down

As the name suggests, pH up and pH down solutions are pH adjusters that can increase or decrease the value of pH in a hydroponic system. These adjusters have specific concentration and can be added without any harm. The pH up adjuster has KOH as an active constituent. When released in the nutrient solution, KOH actively releases OH ions increasing the hydroxyl concentration of the solution- thereby increasing the pH.

The pH down adjuster primarily consists of phosphoric acid H3PO4. The hydrogen ions released from this acid lowers the pH by increasing the hydrogen ion concentration.

Ph Up

pH buffers

pH buffers maintain the value of pH in a hydroponic system. When a buffer is added to a hydroponic system, it works by distributing itself across the solution and then reacting with excessive hydrogen or hydroxyl ions that might disturb the pH value- making them neutral in the process. While choosing a buffer for your hydroponic system, it is imperative to choose one which does not react with the plants’ nutrients or affect their nutritional value.


Maintaining the pH value in a narrow range will allow your hydroponic plants to thrive. To make sure that the pH is in the right range, monitor the pH value after regular intervals using a digital pH meter. pH value can be adjusted using pH buffers, pH up and organic pH down adjusters, or using household chemicals.

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