The Importance of pH in Aquaponics

One important factor for a successful aquaponics system is the proper maintenance of the pH level in the system. Proper maintenance of pH level in aquaponics is essential but tricky because of the three main living components of the system.

Fish, plants, and bacteria have their own ideal pH range. When the pH level is outside of the ideal range, it can cause low plant growth and unhealthy fish, or it could lead to the death of one or more of these living components of the system. 

This article discusses the importance of pH in aquaponics, how it affects plants, fish, and bacteria, and how to maintain and adjust the pH in your aquaponics system.

pH in Aquaponics

The Importance of pH in Aquaponics

Here are some ways pH affects the aquaponic system: 

1. The Impact of pH on plant growth and nutrient uptake
2. The pH level of the water affects the availability and uptake of essential nutrients for plant growth.
3. When pH levels are too high or too low, some nutrients become unavailable, making it difficult for plants to absorb these important nutrients.

The Impact of pH on Fish Health and Growth

The pH level of the water also plays a vital role in the health and growth of fish in aquaponics systems. Fish are sensitive to pH changes, and fluctuations outside the ideal range can cause stress and harm, leading to reduced growth rates, lower disease resistance, and even death.

High pH levels can cause ammonia toxicity, which is harmful to fish, while low pH levels can cause an increase in dissolved carbon dioxide, which can lead to respiratory problems.

Factors That Can Affect pH in Aquaponics

Here are some factors that can impact pH levels in aquaponics:

1. Biological Processes in The System

The biological processes, such as the breakdown of fish waste and the conversion of ammonia into nitrates, can affect pH levels. When fish waste breaks down, it releases ammonia into the water, which can increase the pH level. However, the pH level can decrease as the ammonia is converted into nitrites and then nitrates by beneficial bacteria. So it is crucial to monitor the system's biological processes and adjust pH levels accordingly.

2. Fish Waste and its Breakdown

Fish waste is the main source of ammonia in the aquaponic system, which can increase the pH level. Overfeeding fish can lead to an excess of waste, which can cause pH levels to rise. Regularly removing fish waste and monitoring pH levels can help prevent pH fluctuations.

3. Water Quality and Composition

The composition and water quality used in the aquaponic system can impact pH levels. The pH level of the water source may be naturally high or low, and its composition can also affect pH levels. Testing the water source and making any necessary adjustments can help maintain a stable pH level.

4. Plant Uptake and Respiration

Plants can also influence pH levels in the aquaponic system. During photosynthesis, plants absorb carbon dioxide, which can lower pH levels, and when plants respire at night, they release carbon dioxide, which can increase pH levels. The number and size of plants in the system and the lighting cycle can affect plant uptake and respiration, leading to pH fluctuations. Therefore, it's important to consider plant uptake and respiration when monitoring pH levels in the system.

Monitoring pH in Aquaponics

Here are some critical aspects of monitoring pH in aquaponics: 

1. The Importance of Regular pH Testing

Regular pH testing is essential to monitor the pH levels in an aquaponic system. pH levels can fluctuate due to various factors, such as biological processes, fish waste, water quality, and plant uptake and respiration. Monitoring the pH levels regularly can help aquaponic farmers identify any fluctuations and take corrective measures before they cause significant harm to the system.

2. Methods for Monitoring pH

There are different methods for monitoring pH levels in an aquaponic system, including test kits, pH meters, and continuous monitoring systems. Water test kits are a cost-effective and convenient method for checking pH levels. They come in strips or drops that change color based on the pH level of the water. pH meters provide accurate and precise measurements of pH levels, but they can be expensive and require regular calibration. Continuous monitoring systems use sensors to measure pH levels and provide real-time data, allowing for quick adjustments when necessary.

3. Adjusting pH in the system

If the pH level is outside the optimal range, corrective measures must be taken. 

  • Adding an acidifying agent such as phosphoric acid can effectively lower the pH level.

  • Adding potassium hydroxide or calcium hydroxide can be used to raise the pH level.

It's essential to make these adjustments gradually and closely monitor the pH levels to avoid sudden fluctuations.

What Causes Low pH Levels in Aquaponics?

A low pH level in an aquaponics system can harm the whole system. When the pH level drops, the nitrification process decreases, creating stressful conditions for the fish that often result in fish diseases or death. Several reasons cause the pH level in aquaponics to fluctuate. These are: 

  1. The nitrification process of converting fish wastes into food for the plants has an acidifying effect on the water in the system.

  2. Some water used in the system has a lower pH level to begin with, which can cause problems as the nitrification process runs its course.

  3. The grow media and the materials used in building the system.

  4. The types of plants being grown.

How to Raise the pH Level in Aquaponics?

You can raise the pH level in your system by:

1. Combining equal amounts of calcium carbonate and potassium carbonate adds the mixture to the water. Carbonates are preferred because they will add strength to the carbonate buffer.

2. Another option is to do a water change, as this will help replace the acidic water with more neutral water. Changing the water will prevent immediate damage to your fish and bacteria.

3. Using a grow media that is slightly alkaline, such as crushed limestone, can also help in raising the pH level in your aquaponics system. 

What Causes High pH Levels in Aquaponics?

Too high a pH level in an aquaponics system can cause the nitrification process to stop, which can cause low plant growth in the system. The most common reason for the pH level buildup in aquaponics is the carbonate buildup in the system. These often happen when your water is hard or can be caused by the grow media, materials, or grow beds used in your system. A high pH level is also normal in newly built aquaponics systems, especially those in a cycling stage. 

    pH Water Test in Aquaponics

    How to Lower the pH Level in Aquaponics?

    Several methods can be used in lowering the pH level in an aquaponics system; these are:


    1. In newly built aquaponics systems undergoing the cycling stage, allowing the proper time for the bacteria to establish a bacterial colony is the right way to lower the pH level. This can be done by gradually increasing ammonia levels until nitrite is produced and nitrates are present in the system. Once the system is fully cycled, the water pH level will lower naturally.


    2. Another method to lower the pH level is using certain acids, such as phosphoric acid, which is safe and effective. 

    3. A reverse osmosis (RO) filter can also be used to lower your aquaponics system's pH level. RO filters can remove the carbonates from the water.

    Why Do You Need to Create a Buffer in Your Aquaponics System?

    A buffering agent is a weakly acidic substance dissolved in water to help prevent rapid changes in pH. There are two types of hardness in water, carbonate hardness (KH) and general hardness (GH). 


    However, in aquaponics, we are always concerned with the carbonates because the general hardness of the water affects pH. Still, the buffering capacity (KH) of your water is a more critical pH factor. 

    Carbonates are usually measured on a scale of KH. Measuring your KH level may also help you manage your pH. The larger the KH number, the more resistant your system is to pH changes. A rule of thumb is that if your KH is less than 4 dKH, you don't have the much-buffering capacity and may see rapid or frequent pH swings in your system.

    Here are why you need to create a buffer in your aquaponics system.

    1. Fish cannot handle rapid swings in pH.

    2. Maintaining a buffer is essential for bacterial health because if you get to a point where your carbonates are entirely depleted, your pH level decreases rapidly. Your beneficial bacteria will die quickly, and the biological filtration will stop.

    3. If you don't have a minimum buffer (at least 4 dKH) established in your system, you must manage your pH levels daily and adjust as needed. 

    How to Create a Buffer in Your Aquaponics System?

    You can create a buffer for your aquaponics system by figuring out what your carbonate levels are by getting an API GH and KH Test Kit. If your test results show above 4 dKH, you should be sufficient for now but do a weekly test as part of your regular testing routine. Take note that as your system matures, it will create more nitric acid, so your KH will drop over time. If your dKH fluctuates lower than 4. Adding potassium bicarbonate to your system at a ratio of 2 ½ tsp per 100 gals of system water for each dKH level that you need to go up.


    Proper management of pH is essential in maintaining a successful aquaponics system. So you must consistently monitor the pH levels of your aquaponics system and adjust if needed to ensure that the system functions properly and the plants, fish, and bacteria are healthy. In adjusting the pH level of your system, do it gradually so you will not shock the living elements of your system. By paying close attention to pH levels and taking the necessary corrective measures, you can ensure that your system provides optimal growing conditions for fish and plants.

    3 Responses



    July 16, 2023

    Hi my system pH is recently betwewn 6.0-6.4( according to the test kit reading)
    How to increase the volume of calcium carbonate and potassium carbonate into the water system?
    The ratio between these two components?

    mbeiza delorence

    mbeiza delorence

    January 29, 2023

    this site is an awesome site with good information and useful too. it is well summarised and well established.



    February 08, 2022

    This is very important article ,thank you

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