Water is the lifeblood of an aquaponics system. It is the medium through which fish and plants receive their nutrients and oxygen requirements. So it is essential that every aquaponics grower understands the basic water chemistry to manage an aquaponics system properly.
Monitoring and managing your system's water quality is vital for the health of your fish and plants, as poor water quality can affect the health and productivity of your system. We provide these tips for monitoring the water quality of your aquaponics system for you to get the most out of your plants, fish, and bacteria.
Aquaponics Water Quality Parameters:
pH means “the power of hydrogen,” and it refers to the concentration of hydrogen ions in a solution. pH levels 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.
In aquaponics, it is ideal to keep your pH levels between 6.8 and 7.4, which is the compromise range for the fish, the plants, and the bacteria. This level will keep the bacteria functioning at a high capacity while the plants prefer a more acidic environment.
Monitoring pH regularly is crucial, 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. While a very high pH can cause poor plant growth and poor fruit and flower development.
How to Adjust pH
- To raise pH
In raising the water pH level, use a calcium carbonate and potassium carbonate. You should add equal parts of each at the same time.
- To lower pH
To lower the water pH level in aquaponics, 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.
One of the essential 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, you can increase it by using air stones or a larger pump to increase aeration. Dissolved oxygen levels relate to your water temperature: the warmer the water, the less oxygen it can hold.
The water temperature in your system will affect what type of fish you can raise, the biofilter's performance, and your plant's 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 ability, so it refers to the ability of water to resist a change in pH. Water with low alkalinity is susceptible to pH changes. Water with high alkalinity can resist major changes in pH. Alkalinity is measured by titration (an acid known as “the titrant” is added to the water sample). In aquaponics, the level of alkalinity should be maintained at 100 ppm or above.
Ammonia comes from fish urine, breakdown of solid fish waste, and it is also excreted through the fish gills. In a fish tank, high ammonia levels are toxic to the fish, so it needs to be monitored closely.
Making ammonia and nitrate adjustments for your system.
- High Ammonia Levels - It is ideal to check ammonia levels weekly 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 and 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 and dissolved oxygen levels regularly 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 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 will 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 bedsshould help to lower the nitrate levels in your system.
The water source is the last on this list, but it is a very important parameter in monitoring your water quality. When you’re finished 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. These can be done by purchasing a water purification system, by removing chlorine through aeration, or by leaving the water uncovered in a container for at least 24 hours. You can use a chlorine test to check if your water is chlorine free and safe for your 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 significant 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 again at night if you need to top off more than ⅓ in one day.
- Maintain pH levels between 6.8 to 7.4 for healthy plant growth.
- Removing chlorine and chloramine in your water essential in maintaining a good water quality.
- 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, take note that water quality is vital. You don’t need to be a water expert to monitor your aquaponics system. All you need to be is being responsible for taking measurements using the right equipment and doing what it requires, as stated in those measurements. Subscribe to our Newsletter to receive new updates on our next article.