Water Quality in Aquaponics

Water is the lifeblood of an aquaponics system. It is the medium through which plants and fish receive all the essential nutrients and oxygen requirements. 

To manage an aquaponics system properly, every grower must understand the basic water chemistry to get the most out of plants, fish, and bacteria. This article will discuss the five key water quality parameters and the factors critical to fish, plants, and bacteria health and performance in an aquaponics system.

Aquaponics Water Quality Parameters 

Dissolved Oxygen (DO)

Dissolved oxygen is an essential parameter in aquaponic and is critical to the nitrifying bacteria that convert fish waste into plant nutrients. The recommended DO level for aquaponics is 5 ppm or higher, depending on the fish species being raised. 

Warm-water fish like tilapia and catfish require that the DO not drop below 3 ppm, and cold-water fish species like rainbow trout require that the DO not drop below 4 ppm to maintain good health and optimum growth. In aquaponics, especially in new systems, it is recommended to measure the DO levels frequently (daily), as low DO threatens the health of the fish. 

Factors that can affect DO levels

• Cloudy and rainy days can cause DO to drop because there's less sunlight for the plants to photosynthesize and produce oxygen.
• Too many fish in the fish tank.
• Too much uneaten food is left in the fish tank.
• Saline water.

Two ways to measure DO:

1. By using a DO meter.
2. The colorimetric approach, where the manganese directly reacts with ethylenediaminetetraacetic acid, gives a pink color and can be read using a color meter.

Fish show certain behaviors that indicate low oxygen levels in the water, such as loss of appetite, surface gasping, gathering around inflow pipes, reduced growth, and increased susceptibility to diseases. So if you see these signs and your DO level is too low, you can adjust the DO level by increasing aeration by adding more air stones or using a larger pump.

How Other Water Quality Parameters Affect the Dissolved Oxygen

• The temperature significantly affects the oxygen level of an aquaponics system. High water temperature holds less DO. Colder water can carry more oxygen than warmer water. This is because of the enhanced molecular activity in warm water that pushes oxygen out of the spaces between molecules of the moving water. 
• Water with low PH levels holds lower dissolved oxygen. 
• Dissolved oxygen increases when there is pressure in the water. 

pH

pH is considered one of the most critical water quality variables in aquaponics systems because it influences water quality parameters, such as the ratio of ammonia to ammonium and the solubility of plant nutrients. pH means "power of hydrogen" and refers to the concentration of hydrogen ions in a solution. pH range from 0 to 14, which the range between 0 to 7 is considered acidic, 7 neutral, and between 7 to 14 basic or alkaline.

In aquaponics, it is essential to maintain a pH level that is acceptable to both fish and plants, which is 6.8 to 7.0. So, it is crucial to regularly test the pH levels of your aquaponics system to determine if normal aerobic conditions are present and avoid drastic changes in pH that can affect the plants, fish, and bacteria. 

In a new system, it is recommended to measure the pH levels daily until it becomes stable. Once the system is stable, you can start a less frequent pH measurement, like once or twice a week. There are ways to adjust the pH in aquaponics; these are:

• To raise pH 

Use calcium carbonate and potassium carbonate and add equal amounts of each at the same time.

• To Lower pH

You can use nitric, muriatic, and phosphoric acids to lower the pH in your system. You can adjust the pH by adding acid to the system little by little and wait for it to distribute throughout the system before taking a retest. Repeat the process until your desired pH is achieved.

Water Hardness 

Hardness measures the amount of calcium (Ca) and magnesium (Mg) concentrations in the water and is expressed in ppm calcium carbonate. Water hardness can range from soft (0-75 ppm) to very hard (>300 ppm). In aquaponics, the water hardness should be maintained between 50 and 100 ppm.

The hardness of source water is essential because it affects the buffering capacity of aquaponics systems. Hardness is a measure of dissolved calcium levels and magnesium in the water. The harder the water, means more dissolved minerals are in it. 

There are two types of hardness: general hardness (GH) and carbonate hardness (KH). General hardness is the measure of positive ions. Carbonate hardness is also known as alkalinity, which is the measure of the buffering capacity of water. Carbonate hardness in the water impacts the pH level because KH acts as a buffer to lower the pH.

Well, water is typically hard because of the presence of natural minerals and carbonates. Hard water can be a valuable source of micronutrients for aquaponics and does not affect the living components. Municipal water has lower hardness and is more susceptible to pH swings.

Alkalinity

Alkalinity is a measurement of the water's ability to neutralize acids. It is also called the water's buffering ability to resist pH changes. These buffering materials are called bases, which include calcium carbonate (CaCO3) and bicarbonate (HCO3-) in the water. Water with high alkalinity can resist pH level changes because it contains high carbonate and bicarbonate ions. In aquaponics, water alkalinity should be maintained at 100 ppm.

Ammonia

Ammonia plays a vital role in aquaponics systems. It starts the nitrogen cycle and is the engine of your system's ecology. Fish produce waste that is full of ammonia. Bacteria convert them into nitrites and then nitrates necessary for plant growth.  

Ammonia comes from fish urine breakdown of solid fish waste and is excreted through the fish gills. In a fish tank, ammonia is toxic at high levels, but it is necessary to give plants the system the nutrients they need. 

 Ammonia poisoning in aquaponics fish can lead to: 

• Damage to fish tissues, especially in gills and kidneys.
• Physiological imbalance
• Impaired fish growth.
• Weak resistance to diseases.
• Death

How to Adjust Ammonia Level

Too High Ammonia Levels

Higher ammonia levels occur when more ammonia is produced than can be handled by the biofilters. Possible causes for this are overfeeding of fish, high fish density for the volume of water, or not enough aeration. 

Even if your aquaponics system is stable, it is good to check the ammonia levels weekly to monitor and catch changes early and make adjustments before they become a problem. Below are the methods of adjusting ammonia in aquaponics systems. 

You can Bring Down the Ammonia Levels by‌:

• Checking the pumps and DO levels.
• Adjusting fish feeding rates or the fish density (A rule of thumb is per 2 gallons of water, 1lb of fish). 
• Increasing nitrification efficiency.
• Reducing the quantity of nitrogen going into your system by lowering feeding rates, removing dead fish, and removing uneaten fish feed after feeding. 

Too Low Ammonia Levels

If your system lacks enough ammonia, your plants will not grow. So enough ammonia must be produced and converted into nitrate for your plants to thrive. Low ammonia occurs when there are too few fish in the system or too much water for the number of fish grown. The solution to low ammonia levels is adding more fish to your system, increasing feeding rates, or using a smaller tank.

Water Temperature

The water temperature in the aquaponics system will influence the type of fish that can be raised, plant growth, and the biofilter's performance. Fish are temperature dependents. Warm-water fish species such as goldfish, catfish, and tilapia prefer temperatures ranging from 65° to 85 °F, while cold-water fish species such as trout thrive at temperatures ranging from 55° to 65° F. Water temperature also affects the oxygen level in the water. So it is essential to measure the water temperature regularly.

 

 

Factors that Affect Water Quality in Aquaponics

Water Source

It is essential to know your water source as it can influence your system's water quality. Your potential water source can be well water, surface water, and municipal water. Whatever water source 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.

If you know that your water source has chlorine, you must remove the chlorine before placing fish in your system. You can do this by purchasing a water purification system, removing chlorine through aeration, or 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.  

Settleable Solids

Solid wastes such as uneaten fish food, feces, and other solids can accumulate in the fish tanks over time and settle at the bottom of the tanks. So it is essential to closely monitor your aquaponics system and remove solids and excess fish food after feeding. Unremoved solids will adhere to the plant's roots, decreasing DO levels as they decay. These solids can also negatively affect the nitrifying bacteria, as they require oxygen to convert ammonia into nitrates and clog pipes in the system.  

Carbon Dioxide

High carbon dioxide levels will make fish sluggish and cannot absorb enough oxygen through their gills. The recommended level of carbon dioxide should not exceed 20 ppm. Carbon dioxide is not a problem for systems with diffused aeration because it is vented off to the atmosphere through water agitation.

Testing the Water Quality

Water testing is essential to maintain and confirm excellent water quality in aquaponics systems. Bacteria cannot be seen or measured directly, so water testing is the only way to diagnose bacteria's health and activity. 

In new aquaponics systems, water should be tested daily because the DO, pH levels, ammonia, and nitrate levels must be closely monitored to make daily adjustments until you achieve the desired result. Once the balance is established, you can start cutting your testing back at least once a week. 

There are many simple water quality test kits available such as aquarium test kits or color change test kits, that are reasonably priced but make accurate measurements will work. 

Monitoring Will Help You React Quickly

Keeping an eye on your DO, pH levels, ammonia, temperature, and other factors will help you react and solve the problem immediately before it worsens. If you do not respond quickly once the issue is identified, your fish and plant will suffer or die, which will result in the failure of your aquaponics system. A well-designed and implemented aquaponics system can be efficient. However, it still requires regular monitoring to ensure everything is functioning well. 

 

Tips for Monitoring Water Quality in Aquaponics

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. Here are some tips for monitoring the water quality of your aquaponics system.

1. It's best to add water to the grow bed area instead of directly pouring it into the fish tank. This will lower the chances of mistakes and fatal swings affecting your fish.
2. Don't add or remove more than ⅓ the total volume of water in your system at once. You can do one addition in the morning and again at night if you need to top off more than ⅓ in one day. 
3. Maintain pH levels between 6.8 to 7.4 for healthy plant growth.
4. Removing chlorine and chloramine from your water is essential for maintaining good water quality.
5. 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.
6. 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.

Conclusion

Ensuring excellent water quality in aquaponics is essential for the success of your aquaponics system. Monitoring and maintaining the key water quality parameters such as DO, pH, ammonia, water temperature, and other factors regularly will help you adjust the levels immediately and avoid problems and losses.Water testing is not difficult to do, and there are many water testing kits and meters available to measure these variables. Thank you for reading our article. Subscribe to our mailing list to get regular aquaponics updates.