Tap Water in Aquaponics

The Best pH for Aquaponics Systems

Managing pH levels in an aquaponics system can be tricky because of the three different organisms that must be considered: plants, fish, and bacteria. The success of your aquaponics system comes from the balance between these three organisms. Each organism prefers a different pH range, and it is essential to keep your system in the ideal range. So what are the best pH levels for aquaponics systems?

This blog will cover the basics of pH in aquaponics systems, the best pH level, how it affects the three living organisms, and how to adjust the pH to the ideal level for the fish, plants, and bacteria. 

What is pH in Aquaponics?

pH is the measure of the concentration of hydrogen ions in a solution. It is also referred to as “ the power of hydrogen’. It is a key parameter of water quality and the determining factor in what creatures thrive in the system.

The measurement is charted on a scale ranging from 1 to 14. Pure water has a pH of 7-neutral; if the level measures below 7, it indicates acidity, while it measures above 7, it is basic.

What Are The Best pH Levels in Aquaponics Systems?

The pH level of the water has a significant impact on all the living components of aquaponics, especially on the plants and the bacteria. Plants generally prefer slightly acidic pH levels of 6.0 to 6.5, while fish and bacteria prefer a slightly alkaline pH of 6.0 to 8.5. So to balance the pH needs of the bacteria, plants, and fish in your aquaponics system, you will need to target the best pH range, which is between 6.8 and 7.2. This range will keep the bacteria functioning at full capacity while allowing the plants to fully access the essential nutrients needed to grow.

How to Measure pH in Aquaponics

There are two different ways to measure pH in your aquaponics system. The first and less expensive is by using pH test strips. This way is easy to use, but because the reading is based on a subjective color scale. Inaccurate readings can sometimes make you think that the pH is too high or too low, leading to unnecessary actions. 

The second option is to use a pH meter, which is a little more expensive but accurate. If you have a large-scale system, this is the best option. pH meters contain probes that must be kept wet at all times to avoid damages. 

Factors That Affect pH in Aquaponics

There are several factors (both external and internal to the system) that affect the overall pH of an aquaponics system. pH changes happen inevitably from time to time, but it does not mean that your plants, fish, or bacteria will suffer immediately. But prolonged exposure to poor pH conditions can ultimately bring problems to your system if you do not act immediately.

Here are some factors that can affect the pH levels in your aquaponics system.

  • Water hardness: tap water usually contains minerals and salts that can increase the pH level in the water.
  • Grow media choice: some grow media contain limestone or marble known to increase pH levels.
  • Material used in setting up your system: concrete tanks can elevate the pH level.
  • Water quality: poor water quality can affect the pH levels of your system. Ensure that the water quality of your system is good at all times.
  • New system: new systems are expected to have high pH levels, eventually reducing once your system is fully cycled.
Flood and Drain Aquaponics System

Managing pH in Aquaponics System

There are several techniques for adjusting the pH into your targeted range. pH adjustments should always be performed incrementally to avoid shocking the living organisms in the system and avoid bringing the pH levels into dangerously low or high levels.

  • What Causes a High pH Level?

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 caused by the grow media, materials, or grow beds used in your system. High pH level is also normal in newly built aquaponics systems, especially those in a cycling stage. 

  • How to Lower the pH Level:

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

  1. In newly built aquaponics systems that are 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 particular phosphoric acid, which is safe and effective. 
  3.  Reverse osmosis (RO) filter can also be used in lowering the pH level in your aquaponics system. RO filters can remove the carbonates from the water.
  • What Causes Low pH?

A low pH level in an aquaponics system can be detrimental to the whole system. When the pH level drops, the nitrification process decreases, and it will also create 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 conversion of fish wastes into nutrients for the plants has an acidifying effect on the water. 
  2. The 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.

Whatever the cause of the fluctuating pH level in your aquaponics system, it is essential to bring it back to the ideal range because it can cause problems to the fish, plants, and bacteria in your system.

  • How to Raise the pH Level

Several methods can be used to raise the pH level in aquaponics systems; these can be done by:

  1. Combining equal amounts of calcium carbonate and potassium carbonate and adding 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; this will help replace the acidic water with more neutral water. Changing the water will prevent immediate damage to your fish and bacteria.
  3. You can also add sodium hydroxide to raise the pH level of the water in your system.
  4. Using a grow media that is slightly alkaline, such as crushed limestone, can also help in raising the pH level in your aquaponics system. 


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.