Aquaponics Maintenance: Monitoring Water Quality

Water is the largest and one of the most important components of an aquaponics system. Water is considered to be the lifeblood of an aquaponics system. The quality of the water in an aquaponics system is essential because it ensures the growth of healthy fish and plants.

Aquaponics pH Water Test

Water quality consists of important parameters including pH, dissolved oxygen, water temperature, alkalinity, ammonia level and water source. A good understanding of how these parameters relate with each other is important to maintain a balanced aquaponics system.

Aquaponics Water Quality Parameters:


pH in water stands for "the power of hydrogen," and it refers to the concentration of hydrogen ions in a solution. Water pH can range from 0 to 14, with 7 being neutral. The values between 0 and 7 are acidic, while the values between 7 and 14 are basic or alkaline. 

It is important to maintain the water pH at levels that are acceptable to the plants and fish. In aquaponics, it is ideal to keep your pH levels between 6.8 and 7.4, which is the compromise for the fish, the plants, and the bacteria. This range will keep the bacteria function at high capacity while the plants prefer a more acidic environment. 

Monitoring pH regularly is very important, as a sudden change in pH levels can be lethal to both the fish and plants. If pH levels in your system get too low, the nitrification will slow down or stop, and ammonia will accumulate to a level that is toxic to the fish. A very high pH can cause poor plant growth and poor fruit and flower development.

How to Adjust pH

  • To raise pH

To raise water pH, it is recommended to use calcium carbonate and potassium carbonate and to add equal amounts of each at the same time. 

  • To lower pH

To lower pH, it is recommended to use certain acids, such as nitric, muriatic, and phosphoric. Phosphoric is the safest of the three acids. Rapid pH changes can be harmful to the fish, so adjust and add to the system little by little and wait for it to distribute throughout the system before taking a retest. You can repeat until your desired pH level is achieved. 

Dissolved Oxygen

One of the most important parameters for raising fish is the dissolved oxygen (DO) in the system.

Dissolved oxygen levels should be maintained at 5 ppm or higher in most aquaponics systems. In a new system, dissolved oxygen should be measured frequently, but once the system is established, you can measure it less regularly.

Low levels of dissolved oxygen arise more in commercial aquaponics with high stocking rates of fish than in small systems with low fish stocking rates. If the dissolved oxygen is too low in your system, you can useair stones or switch to alarger pump to increase aeration. Dissolved oxygen levels relate to your water temperature: the warmer the water, the less oxygen it can hold. 

Water Temperature

The water temperature in your system will affect what type of fish you can raise, the performance of the bio-filter, and your plants' growth.

Fish are temperature dependent. Goldfish, tilapia, bass, and catfish are warm-water fish and prefer a temperature ranging from 65° to 85°F while trout are cold-water fish and thrive in temperature ranges of 55° to 65°F. Your water should be the right temperature for the fish for optimum growth and to avoid fish diseases. 


Alkalinity is a measurement of water's ability to neutralize acids. It is also called water's buffering capacity, so it refers to the ability of water to resist a change in pH. Water with low alkalinity is susceptible to changes in pH, while water with high alkalinity can resist major changes in pH. Alkalinity is measured by titration (an acid known "the titrant" is added to the sample of water). In aquaponics, the level of alkalinity should be maintained at 100 ppm or above.

Aquaponics Water Test

Ammonia Level

Ammonia comes from fish urine, breakdown of solid fish waste, and it is also excreted through the fish gills. In a fish tank, you need to closely monitor the ammonia level because high ammonia levels are toxic to the fish.

To learn more about ammonia and the importance of beneficial nitrifying bacteria's role in an aquaponics system, checkout Bacteria's Role in Aquaponics: Is Bacteria Good For My Aquaponics System?

Making ammonia and nitrate adjustments for your system.

  • High Ammonia Levels - It is ideal to check ammonia levels every week to see changes quickly and to make adjustments before they become a big problem for your system. The cause of higher ammonia in an aquaponics system is overfeeding the fish, a fish density that is too high for the volume of the water (1 lb of fish per 2 gallons of water is a rule of thumb), or not enough aeration. You should check your pumps, dissolved oxygen level, and adjust your feeding rates or fish density if the ammonia levels in your system are too high. 
  • Low Ammonia Levels - If there is not enough ammonia being produced in your system, your plants will not grow. Low ammonia occurs when there is not enough fish, or there is too much water for the number of plants being grown in your system. Adding fish to your system, feeding them right, or using a smaller tank should solve this problem. 
  • High Nitrate Levels - High levels of nitrites could be a sign that not enough plants are being grown to consume all the nitrates that are produced by the nitrifying bacteria. Adding more plants to the grow beds or adding more grow beds should help to lower the nitrate levels in your system. 

Water Source

The water source is the last on this list, but it is a very important parameter in monitoring your water quality. When you're done building and planning your aquaponics system, the first thing you need to do is to fill it up with water. 

It is important to know your water source as it can influence the water quality of your system. Your potential water source can be well water, surface water, and municipal water. Whatever source of water you use, it is essential to test it for a water quality profile to ensure that your water meets your fish and plant water requirements.

Your water should be in the pH range of 6.8 to 7.4. If you know that your water source has chlorine, you must remove the chlorine before placing fish in your system. This can be done by purchasing awater purification system, by removing chlorine through aeration, or by leaving the water uncovered in a container for at least 24 hours. You can use achlorine testto check if your water is chlorine-free and safe for you fish, plants, and bacteria. A safe level of chlorine is less than 1 ppm. 

The most important thing to remember in adjusting water parameters is to make small adjustments. Making large adjustments quickly could cause an undesirable and irreversible effect on your aquaponics system.

Tips for Monitoring the Water in Your Aquaponics System

  • It's best to add water to the grow bed area than directly into the fish tank. This will lower the chances of mistakes and fatal swings that could affect your fish. 
  • Don't add or remove more than ⅓ the total volume of water in your system at one time. You can do one addition in the morning and one at night if you need to top off more than ⅓ in one day. 
  • Maintain a pH level between 6.8 to 7.4 for healthy plant growth.
  • Removing chlorine and chloramine in your water is very important in maintaining a healthy aquaponics system. 
  • In a newly built aquaponics system, water should be tested daily, so adjustments can be made as soon as possible and weekly in an established system.
  • Record all your readings in a paper or journal. So you can check your records and will know immediately if there are changes in your water quality. 


Whether you're starting a new system or adding water to your existing aquaponics system, water quality is very important. You don't have to be a water scientist or engineer to monitor your system. All you need to be is being responsible for taking measurements by using the right equipment and doing what it requires, as stated in those measurements. Subscribe to our newsletter for more information about aquaponics.

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