Mastering the Aquarium Nitrogen Cycle: Fish Tank Cycling Made Easy

The process of converting harmful ammonia into nitrite and finally into nitrate is known as the fish tank cycling process. During this cycle beneficial bacteria colonies grow.

Nitrifying bacteria are all around us and in the water. Bottled ammonia and’seeding’ with used filter media can speed up the cycling process but are not necessary as the bacteria will grow on their own.

Aquarium Nitrogen Cycle

The Aquarium Nitrogen Cycle is the process by which waste from fish and plants are broken down into ammonia and then converted to nitrite and finally to nitrate. This process takes place in a freshwater aquarium, saltwater aquarium, reef tank, or even a pond. It is a very important and complex process that all fish-keepers need to be aware of.

Ammonia is generated from fish feces and uneaten food. It is toxic to fish at levels over 2 ppm. Ammonia is oxidised by Nitrosomonas bacteria to form nitrite. Nitrites are also toxic to fish at concentrations above 1 ppm. Nitrites are oxidised by Nitrobacter bacteria to form nitrates which are less toxic to fish.

The nitrates are then absorbed by plants and used as nutrients. This is a completely natural process and it will happen in every type of aquarium. However, it is a very slow and sometimes difficult process. It is not uncommon for a new thiet ke be hai san cho nha hang aquarium to take up to a month before ammonia, nitrite and nitrate concentrations are stable. It is crucial that the aquarium is kept clean to allow these beneficial bacteria to grow. Over cleaning a tank can hinder this process and result in ammonia, nitrite and/or nitrate spikes. A good quality API Master Test Kit is essential for monitoring your aquarium’s water parameters.

 

Fishless Cycling Method

Traditionally, cycling a fish tank involves adding a few hardy fish to the aquarium to jump start the process. Unfortunately, this is cruel and inhumane. The fish may survive but their gills are burned by the rising ammonia levels, and it will have a negative impact on their quality of life. Using a fishless cycle eliminates this step and provides the best environment for the bacteria to grow.

There are two ways to do a fishless cycle: 1) Seeding the tank with established bacteria colonies that will colonize the new tank. This method takes a similar amount of time as traditional cycling but is much more fish-friendly and does not have the same consequences on the water quality. 2) Using a product like Septo-Bac to speed up the cycling process. This will also take a similar amount of time as traditional cycling and may not be effective in every situation.

During the fishless cycle, it is important to monitor the ammonia and nitrite levels regularly. If the level of ammonia spikes, it will likely be a sign that the bacteria are not fully established. If the ammonia drops to zero and nitrites rise, it is a good sign that the cycle is complete. It is also important to perform regular water changes during the fishless cycle to ensure that there is sufficient ammonia in the water for the bacteria to thrive.

Aquarium Beneficial Bacteria

Biologically speaking, cycling occurs when resident populations of nitrifying bacteria in an aquarium are large enough to process the full bioload (exceedingly poisonous ammonia and nitrite) as they are produced. This is why it is important to stock a tank slowly over time rather than adding a significant amount of fish all at once.

Those nitrifying bacteria can actually live on any surface in an aquarium, but they tend to concentrate their colonies where the limiting factors (food and oxygen) are best met. The porosity of the filter media provides a huge surface area for these microorganisms to grow and they thrive in the flow of water passing through the filter. The bacterial colonies in the biomedia outcompete bacteria elsewhere in the aquarium, consuming ammonia and nitrite as fast as they are produced and making them undetectable.

In the wild, these nitrifying bacteria are found in both the water column and sediment. However, the majority of nitrifying bacteria are housed in the biofilm. It is difficult to cultivate pure cultures of these bacteria and this likely accounts for the common misconception that nitrifying bacteria only lives in the filter. A recent study by LI et al (2018) demonstrated that the ammonia-oxidising bacteria (AOB) and the nitrite-oxidising bacteria (NO3) do indeed live in the water column. These bacteria can be introduced into a new aquarium using products like API Quick Start, Fritzzyme Turbostart or Tim’s Aquatics Live Nitrifying Bacteria and can speed up the aquarium cycle considerably.

Steps to Cycle a New Fish Tank

When you set up a new aquarium, whether you are using live rock or a bare bottom tank the first thing that needs to be done is seeding it with beneficial bacteria. This can be accomplished with products like Tetra Safe Start or a freshwater master test kit. Once this step has been completed you can move on to adding the rest of your equipment and filling the aquarium with water.

This will begin the cycle, the process of creating a population of beneficial bacteria that regulates the nitrogen cycle in the aquarium. During the cycling process ammonia will rise and fall, then nitrite and finally nitrate. Once all of these are at 0 ppm then the aquarium is ready for livestock to be introduced.

During the cycling process it is important to regularly test the water, checking for ammonia, nitrite and nitrate. If you see nitrate build up it is recommended to add one tablespoon of table salt or aquarium salt for every 10 gallons of water. This will reduce nitrate toxicity and allow the beneficial bacteria to grow faster.

Another important factor to remember is that the aquarium should never be fully stocked during this process. If you add fish too soon, the ammonia levels will quickly increase and this is toxic to the fish.