How often should aquaponics cycle?

The rule of thumb for aquaponics is to conduct cycling before adding the fish and plants into your chosen system. Developing a bacterial colony in new aquaponics systems is known as system cycling. When the nitrate levels progressively grow, and the ammonia level is within the recommended range, your new aquaponics system is considered fully cycled.

What is cycling in aquaponics?

One of the most challenging aspects of setting up an aquaponics system is "cycling." This process describes establishing the nitrogen cycle in an aquaponic system by colonizing it with nitrifying bacteria. When ammonia is available, the bacteria required for colonization will begin to appear. In short, cycling is the process of preparing your system for the entrance of microorganisms that convert ammonia and ammonium to nitrites and finally nitrates.

Why should aquaponics undergo cycling?

Fish excrete waste, which microbes convert to plant nutrients. However, if you start the system with fish and plants right away, there will never be any bacteria to transform the fish waste.

Cycling encourages bacteria that convert fish waste to nitrates to arrive and multiply. When starting up your aquaponics system, cycling is a must to ensure that all necessary components for effective plant development are present.

What are the two types of cycling for an aquaponics system?

Cycling with fish

This type is the most established and can last from 25 to 40 days. The prolonged process for this cycling is based on the fact that there is a slow introduction of nitrifying bacteria. Here are steps to observe for cycling your aquaponics while there are fish in the tanks:

  1. Add a few fish to the fish tank to begin the fish cycle process. Only add a few fish because too many will cause ammonia levels to rise, causing injury to the fish.
  2. Once your fish have been introduced, feed them lightly to encourage them to produce waste, initiating the cycle.
  3. Daily check the ammonia, nitrite, and nitrate levels to ensure they are within the acceptable range. To avoid an ammonia spike, you must do a partial or complete water change. This applies if the ammonia level exceeds 3.0 ppm. Remember, as well, that the nitrite level should be kept below 1.0 ppm, and the nitrate level should rise over time.
  4. Continue to check ammonia, nitrite, and nitrate levels and replace water as needed until your fish tank is completely cycled. When your ammonia and nitrite levels are below 0.25 ppm, your aquaponics system has cycled fully.

Cycling without a fish

This cycling is the opposite of the first one. Fishless cycling has gained a significant number of practitioners, making it the most utilized way of cycling. One of the things that makes it a popular choice is that it only takes a few days to complete.

Fishless cycling also benefits the fish. First, the grower and the fish will be less stressed during the process. Second, because no fish are involved in the process, there are fewer concerns for ammonia, nitrite, or pH levels to rise.

At this point, you might be asking, "How do you introduce ammonia in a fishless system?" I shortlisted my answers below:

  1. Ammonium chloride: This works like how liquid ammonia does. Ammonium chloride is readily available at any aquarium supply store.
  2. Urine: As awkward as it may seem, ammonia is present in human and animal urine, and it can be used in cycling an aquaponics system. If you decide to make use of urine as an ammonia source, keep it in a sealed bottle for three weeks to allow it to convert to ammonia before introducing it to your system. Your ammonia levels will initially be relatively low with fresh pee, but they will suddenly rise or burst after a few weeks, which is not advisable.
  3. Liquid ammonia: For growers who will use this chemical, be sure it is pure (at least 5-10 percent ammonia) and that the only other ingredient is water.
  4. Dead fish: This source is the least advisable to use. Flies and other insects may be attracted to dead fish, which is not good. Using a dead fish as an ammonia source is not recommended due to the risk of introducing additional germs or chemical substances into your system.

Here are steps for fishless cycling:

  1. When your aquaponics system is ready, start by slowly adding an ammonia solution to the fish tank. Continue doing this until the ammonia test reading reaches -5 ppm.
  2. Keep track of how much ammonia it took to get to -5 ppm and add that amount daily until the nitrite level reaches 0.5 ppm.
  3. Experienced growers recommend reducing the daily dose of ammonia to half of the original volume when nitrites appear.
  4. Your system is fully cycled when nitrates reach 5 to 10 ppm, and nitrites reach zero, then you may begin adding fish.

What are the factors to consider in cycling an aquaponics system?


Temperature affects both types of bacteria, considering that they are microorganisms. Their ideal temperature range for growth is between 77 and 86 degrees Fahrenheit (25 and 30 degrees Celsius). Anything outside of this range will have an impact on dissolved oxygen levels and bacteria's capacity to digest waste.

Chlorine and chloramines

It is imperative that any water utilized in your aquarium aquaponics system be properly dechlorinated. If not removed from the water, chlorine and chloramines used in city water systems are toxic to aquatic life and kill fish. Before introducing fish or microorganisms to any aquarium, the chlorine must be thoroughly neutralized.

Dissolved oxygen

Maximal nitrification rates can be achieved at dissolved oxygen (DO) levels greater than 80% saturation. If your dissolved oxygen is below 2.0 mg/l (ppm), nitrification will not take place. Nitrobacter is more affected by low DO than Nitrosomonas, which increases the levels of harmful nitrites in the water.

pH range

The nitrification process is also influenced by pH. If the levels are below 7.0, this will have a negative effect on bacterial performance, which is entirely inhibited at pH 6.0. Nitrobacter prefers a pH range of 7.3-7.5, while Nitrosomonas prefers 7.0-8.0.


Nitrifying bacteria are sensitive to light, particularly ultraviolet and blue light. During the cycling process, turn off any UV-emitting bulbs. On the other hand, any standard aquarium illumination will have no discernible negative impact.

What happens when you cycle an aquaponics system too often?

When setting up or restarting an aquaponic system, cycling begins. The time frame is determined by the water temperature (between 75 and 80 degrees Fahrenheit or 24 and 26 degrees Celsius). In most cases, the cycle process takes 4-6 weeks.

It is not recommended to cycle your system again and again because you are disrupting the harmony already present. Unless you need to move your fish into a bigger aquaponics setup, that you will have to establish the nitrogen cycle, you do not need to cycle too often.


To provide the best environment for your fish, plants, and microorganisms, you will need to cycle to cycle your aquaponics system. It cannot be easy, but it is an essential component of the setup procedure. You have to cycle the system once, so you will not have to deal with it regularly. However, after your new system has cycled successfully, all you have to do now is maintain it, plant your favorite crops, harvest, and enjoy the results of your labor.

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