Aquaponics Glossary: Fishless cycling


Aquaponics Glossary: Fishless cycling
A fishless aquaponics system

Welcome to our comprehensive guide on fishless cycling in aquaponics. In this article, we will delve into the intricacies of this crucial process and provide you with a step-by-step guide, insights into the different types of bacteria involved, the benefits and advantages of fishless cycling, common mistakes to avoid, the roles of ammonia and nitrite, monitoring water parameters, the duration of the fishless cycling process, troubleshooting common issues, alternative methods for jumpstarting the nitrogen cycle, and understanding the relationship between plants and bacteria during fishless cycling. Let’s get started!

Understanding Fishless Cycling in Aquaponics

Fishless cycling is an essential process in aquaponics that establishes the beneficial bacteria necessary to convert toxic ammonia into nitrite and ultimately into nitrate. This cycling is necessary to create a stable and healthy environment for both the fish and plants in your aquaponic system. By simulating the natural nitrogen cycle through fishless cycling, you ensure the establishment of a balanced ecosystem without the risk of harming fish during the initial setup stages.

During fishless cycling, ammonia is typically introduced into the system through the addition of a source such as pure ammonia or fish food. As the ammonia levels rise, certain types of bacteria, known as nitrifying bacteria, begin to colonize the system. These bacteria convert the ammonia into nitrite, which is still toxic to fish. However, another type of bacteria, called nitrite-oxidizing bacteria, then convert the nitrite into nitrate, which is much less harmful to fish.

The Importance of Fishless Cycling in Aquaponics Systems

Fishless cycling plays a vital role in aquaponics systems as it establishes a stable environment for the fish and plants to thrive. By allowing the beneficial bacteria to colonize and convert ammonia and nitrite, fishless cycling helps maintain water quality and prevents the accumulation of harmful substances that can compromise the health of the organisms within the system. It is a crucial step that sets the foundation for a successful aquaponic setup.

One of the key benefits of fishless cycling is that it allows aquaponics system owners to introduce fish gradually, reducing the risk of stress and potential fish loss. By cycling the system without fish initially, the water parameters can be carefully monitored and adjusted as needed before adding fish. This gradual approach helps to ensure that the fish are introduced to a stable and healthy environment, minimizing the chances of shock or disease.

In addition to establishing a stable environment, fishless cycling also helps to optimize the growth and productivity of the plants in the aquaponics system. The beneficial bacteria that develop during the cycling process play a crucial role in breaking down ammonia and nitrite, which are byproducts of fish waste. By converting these harmful substances into nitrate, the plants can then utilize this nutrient-rich compound for growth. This symbiotic relationship between the bacteria and plants creates a self-sustaining ecosystem where the plants thrive and help to maintain water quality for the fish.

Step-by-Step Guide to Fishless Cycling in Aquaponics

When embarking on fishless cycling in your aquaponics system, it is essential to follow a step-by-step process for optimal results. Here is a comprehensive guide to help you through each stage:

  1. Start by adding a source of ammonia to the system, such as fish food, pure ammonia, or liquid ammonia.
  2. Monitor ammonia levels regularly using a reliable test kit.
  3. As ammonia levels rise, the first type of bacteria, Nitrosomonas, will establish itself and convert ammonia into nitrite.
  4. Continue monitoring ammonia and nitrite levels while providing a constant source of ammonia.
  5. As nitrite levels increase, the second type of bacteria, Nitrobacter, will colonize your system and convert nitrite into nitrate.
  6. Test and monitor nitrate levels, ensuring they reach a steady state.
  7. Once ammonia and nitrite levels decrease, and nitrate is consistently present, the fishless cycling process is complete, and your system is ready for fish and plants.

It is important to note that the duration of the fishless cycling process can vary depending on several factors, including the size of your aquaponics system and the efficiency of the bacterial colonization. Generally, it can take anywhere from 2 to 6 weeks for the cycling process to complete.

Types of Bacteria Involved in Fishless Cycling

The success of the fishless cycling process relies on the presence and activity of specific bacteria. Nitrosomonas bacteria are responsible for converting ammonia into nitrite, while Nitrobacter bacteria convert nitrite into nitrate. Understanding these bacterial processes and providing the necessary environment for their growth is essential for establishing a healthy aquaponic system.

In addition to Nitrosomonas and Nitrobacter bacteria, there are other types of bacteria that play a role in fishless cycling. One such bacteria is Nitrospira, which is responsible for further converting nitrite into nitrate. This conversion is important as nitrate is the least toxic form of nitrogen and can be safely utilized by plants in the aquaponic system. Another type of bacteria, called heterotrophic bacteria, also contribute to the cycling process by breaking down organic matter and converting it into ammonia. These bacteria help maintain a balanced nitrogen cycle and ensure the overall health of the system.

Benefits and Advantages of Fishless Cycling in Aquaponics

Fishless cycling offers several benefits and advantages in aquaponics systems. Firstly, it eliminates the risk of harming fish during the initial setup phase. Secondly, it allows for precise control of ammonia and nitrite levels, ensuring a safe and stable environment for the organisms in the system. Additionally, fishless cycling establishes a robust ecosystem, promoting optimal plant growth and high fish production.

One of the additional benefits of fishless cycling is that it reduces the overall cost of setting up an aquaponics system. Without the need to purchase and maintain fish, the initial investment required for fishless cycling is significantly lower. This makes aquaponics more accessible to individuals or organizations with limited financial resources.

Furthermore, fishless cycling allows for greater flexibility in system design and operation. Since there are no live fish involved, the system can be easily modified or expanded without the need to consider the specific requirements and compatibility of different fish species. This flexibility enables aquaponics practitioners to experiment with different plant and fish combinations, optimizing the overall productivity and efficiency of the system.

Common Mistakes to Avoid during Fishless Cycling in Aquaponics

While fishless cycling is a relatively straightforward process, there are common mistakes that can hinder its success. These mistakes include overfeeding the system with ammonia, failing to monitor water parameters regularly, not providing a constant source of ammonia, and adding fish before the cycling process is complete. By avoiding these errors, you increase the likelihood of a successful fishless cycling experience.

One additional mistake to avoid during fishless cycling in aquaponics is not properly adjusting the pH levels of the water. Maintaining the correct pH range is crucial for the growth and health of both the beneficial bacteria and the plants in the system. If the pH is too high or too low, it can inhibit the growth of the bacteria or affect the nutrient uptake of the plants. Regularly testing and adjusting the pH levels will help create an optimal environment for the cycling process and ensure the success of your aquaponics system.

The Role of Ammonia in the Fishless Cycling Process

Ammonia is the primary substance involved in fishless cycling. It serves as the source of nutrition for the initial group of bacteria responsible for breaking it down into nitrite. By carefully controlling and monitoring the levels of ammonia, you create an environment conducive to the growth and establishment of beneficial bacteria in your aquaponic system.

Nitrite Accumulation and its Significance during Fishless Cycling

As ammonia is converted into nitrite during fishless cycling, it is crucial to monitor nitrite levels closely. Nitrite is highly toxic to fish and plants and can cause significant harm if it accumulates to high concentrations. Nitrite serves as an indicator of the progression of the cycling process and the establishment of the necessary Nitrobacter bacteria, which convert it into nitrate, a significantly less harmful substance.

Monitoring Water Parameters during Fishless Cycling in Aquaponics

Regular monitoring of water parameters is essential during fishless cycling. Key parameters include ammonia, nitrite, nitrate, pH, and temperature. By using reliable test kits and maintaining optimal conditions, you can track the progression of the cycling process and address any issues that may arise promptly.

How Long Does Fishless Cycling Take in Aquaponics?

The duration of the fishless cycling process can vary depending on various factors, including temperature, ammonia source, and the efficiency of bacterial colonization. On average, fishless cycling takes approximately 4 to 8 weeks to complete. However, it is crucial to monitor water parameters and wait until ammonia and nitrite levels stabilize before introducing fish and plants to your aquaponic system.

Troubleshooting Common Issues during Fishless Cycling

During fishless cycling, you may encounter common issues that can hinder the progress of the process. Some potential problems include high ammonia or nitrite levels, a lack of bacterial colonization, fluctuating water parameters, or slow cycling progress. By understanding these issues and taking appropriate corrective measures, you can overcome obstacles and ensure a successful fishless cycling experience.

Alternative Methods for Jumpstarting the Nitrogen Cycle in Aquaponics

While fishless cycling is the most common method for jumpstarting the nitrogen cycle in aquaponics, there are alternative approaches you can consider. One method involves introducing hardy fish species that can tolerate the initial high ammonia and nitrite levels while facilitating the cycling process. Another option is using filter media or water from an established aquaponic system to introduce beneficial bacteria. These alternatives can help expedite the establishment of a stable nitrogen cycle.

Understanding the Relationship between Plants and Bacteria during Fishless Cycling

Plants play a vital role in the fishless cycling process. As bacteria establish themselves and convert ammonia and nitrite into nitrate, plants utilize the nitrate as a nutrient source, completing the nitrogen cycle. The presence of healthy plants aids in balancing nutrient levels in the system and contributes to the overall success of fishless cycling in aquaponics.

Assessing Nitrifying Bacteria Colonization during Fishless Cycling

To assess the colonization of nitrifying bacteria during fishless cycling, regular monitoring of water parameters is crucial. By testing ammonia, nitrite, and nitrate levels, you can evaluate the progress of bacterial establishment and ensure that the cycling process is moving in the right direction. Additionally, monitoring plant health and growth can serve as an indicator of the overall success of the fishless cycling process.


In conclusion, fishless cycling is a critical step in establishing a healthy and balanced aquaponic system. By understanding the process, the types of bacteria involved, and the factors to monitor, you can ensure a successful cycling experience. Take your time, be patient, and follow our step-by-step guide for optimal results. Soon enough, you will have a flourishing aquaponic system that provides an abundant harvest of both fish and plants.