Do I need to change the water in aquaponics?

Aquaponics is identified as a type of recirculating aquaculture system (RAS), where water in the system travels across its major sections perpetually. Ideally, there is no need to change the water in aquaponics since the plants act as filters that cleanse the water returning to the fish tanks. But in some cases, the grower would be compelled to replace or add water into the system. This article discusses such situations and the proper procedure for doing so.

Does aquaponics experience water loss?

Water is one of the essential elements of aquaponics. This element functions by transporting crucial nutrients from the fish excrement to the grow beds and aids in facilitating plant growth. Aquaponics requires a lot of water when it is first set up, but over time, thanks to the recirculation process, it uses less of it than traditional soil gardening.

The process of recirculation in an aquaponic unit yields 95 to 99 percent water re-use efficiency, according to a study by the University of Gothenburg. Despite constant use, the system's water quality is preserved, and fewer than 100 liters were used for every kilogram of fish.

Even if an aquaponic system uses water more effectively, it still loses water from setup issues and natural causes. The good news is that this soilless technique can result in very little water loss.

Another study on the energy and water usage of a small-scale raft aquaponics system revealed that a non-commercial unit requires an average of 35,950 liters for top-off per year and only loses 1% of its water daily. Evapotranspiration and leaks were to blame for the measured water loss.


Water is used by plants and evaporated through a process called evapotranspiration. Evapotranspiration cannot be stopped because it is vital to all living things. However, by ensuring that your temperature range is suited for the crops you are cultivating, you can maintain it as biologically effective as possible.

System leaks

The irrigation system for aquaponics setups occasionally develops leaks. A leaf or a dislodged dripper may redirect the water flow, but it's more likely that there is a broken pipe or split tubing. Leaks are easiest to find when the system is carefully and frequently monitored. Three times a day, we go through our greenhouse to look for leaks, and when we find them, we swiftly fix them.

Should you change the water in aquaponics?

Changing the water of an aquaponics system is possible. When there are severe algae problems, changing the water is primarily necessary. Algae can be a serious issue since it can negatively influence your aquaponics fish tank's natural pH and the nutrients your plants need.

There are two practical ways that you can do to solve possible severe algae problems:


This step is the quickest and most straightforward technique to eliminate algae in your system. For growth and reproduction, green algae require light. Your tanks can either be shaded or covered with a dark-colored cloth or a piece of plastic.

As this can reflect the sun and keep water from heating up, many growers paint sump tanks and any translucent plastic black with white paint applied on top.

In media beds, you can shade by adding more rock or gravel to prevent light from reaching the damp parts if you have algae problems on the surface of your media bed or Bato buckets.

Mechanical filtration

Algae eradication can be significantly aided by mechanical filtering. To eliminate algae in your system, employ filters, screens, vortexes, or centrifugal settling equipment. Despite being simple to construct, the equipment can be pricey.

If you are utilizing media-based aquaponics, your system's grow bed will function as a sizable mechanical filter and remove algae from your water.

How do you change the water in aquaponics?

If you decide to change the water in your aquaponics, here are a couple of steps that you can observe:

  1. If the reason for water replacement is too much water evaporation due to high temperature and strong winds, then identify how much water was lost from your fish thanks.
  2. If the reason for changing the water is algae growth, then removal of the affected portion of the volume of your tanks is recommended. Any food scraps and fecal matter that are on the substrate should also be siphoned.
  3. Replace the water you have removed with tap water or rainwater around the same temperature as the fish tank's water. If using tap water, dechlorinate at all times.

What important water quality parameters in aquaponics should you maintain?

Dissolved oxygen

All three species in aquaponic systems—plants, fish, and nitrifying bacteria—need oxygen to survive. The molecular oxygen content of the water is indicated by the dissolved oxygen (DO) level, which is expressed in milligrams per liter. Indeed, a low level of DO is fatal to your fish. Therefore, maintaining sufficient DO levels is essential for aquaponics.

Directly from the atmosphere, oxygen dissolves on the surface of the water. Fish can survive in this water under natural circumstances. Still, in intensive production systems with increased fish densities, there is not enough DO diffusion to meet the needs of the fish, the plants, and the bacteria. Therefore, managerial techniques must be used to supplement the DO:

  1. Water pumps
  2. Aerators

pH level

Management of aquaponic systems benefits from having a basic understanding of pH. On a scale from 1 to 14, the pH of a solution determines how acidic or basic the solution is. Anything with a pH of 7 or higher is neutral; anything with a pH lower or higher than 7 is acidic. The quantity of hydrogen ions (H+) in a solution is called pH; the more hydrogen ions present, the more acidic the solution.

The pH of the water significantly impacts the plants and bacteria. The pH affects a plant's ability to obtain micro-and macronutrients. All the nutrients are easily accessible at a pH between 6.0 and 6.5; however, plants find it challenging to obtain the nutrients outside of this range. An iron, phosphorus, and manganese nutritional deficiency might result from a pH of 7.5. Nutrient lockout is the name of this occurrence.

Below a pH of 6, nitrifying bacteria struggle, and acidic, low pH circumstances decrease the bacteria's ability to convert ammonia into nitrate. As a result, the bacteria's ability to convert ammonia to nitrate may decline, ammonia levels may start to rise, and the biofiltration process may be compromised, creating an unstable environment that is harsh to other organisms.

Although most fish utilized in aquaponics have a pH tolerance range of 6.0-8.5, fish also have unique pH tolerance ranges. However, the toxicity of ammonia to fish is influenced by pH, with higher pH resulting in more significant toxicity.


In aquaponic systems, water temperature affects the fish that can be raised and plant growth and biofilter function. The temperature affects different fish species. While coldwater species like trout thrive at temperatures between 55°F and 65°F (13 and 18 °C), warm water species like goldfish, bass, catfish, and tilapia would thrive at temperatures between 65 and 85°F (18 and 29 °C). For optimum growth, tilapia prefer temperatures between 81 and 85 °F (27 and 29 °C). Below 70 degrees Fahrenheit (21 °C), growth slows down significantly, reproduction halts, and illness incidence rises.

Water hardness

Hardness and alkalinity are frequently mistaken. Hardness, which is measured as the equivalent of calcium carbonate in parts per million (ppm), indicates how much calcium (Ca) and magnesium (Mg) are in the water. Alkalinity, which varies from soft water (0 to 75 ppm) to very hard water (>300 ppm), is the measure of the water's calcium carbonate (CaCO3) and bicarbonate (HCO3) content.

Water for aquaponics should contain an adequate amount of calcium, magnesium, carbonate, and bicarbonates. In other words, water needs to be kept at 100 ppm calcium carbonate or more in water that is moderately hard or harder.

Was this post helpful?

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram