from the blog

The Nitrogen Cycle in Your Aquarium

Care and maintenance

Water quality

September 28, 2020

Newly started fish tank

Even if you are new to the aquarium hobby you are probably familiar with the nitrogen cycle. Perhaps you have heard it referred to as the start-up cycle, the nitrification process or even new tank syndrome. Regardless what you call it, the nitrogen cycle is a very important process for the aquarium hobbyist to understand. Unless you understand  how this cycle works you may have trouble maintaining high water quality in your tank and your tank inhabitants could suffer as a result.

What is it?

Simply put, the nitrogen cycle is the biological process through which beneficial bacteria in your aquarium break down organic wastes and harmful substances like ammonia and nitrite, turning them into less harmful substances called nitrate. As your tank inhabitants eat and excrete waste, a layer of organic debris builds up in the substrate of your tank. This organic debris may include more than just excrement – it may also include uneaten fish food, decaying plant matter and even dead fish, if you do not clean your tank often enough. As this debris breaks down, a substance called ammonia is produced and released into your tank water. The nitrogen cycle, then, is the process by which aquatic bacteria convert that ammonia into a less harmful substance called nitrate.

The Three Stages

The first stage of the nitrogen cycle is the one in which ammonia is introduced into the tank by means of the breakdown of organic waste. As this organic waste breaks down, it forms either ionized ammonium (NH4) or un-ionized ammonia (NH3). While ammonium is not toxic to aquarium fish, ammonia is very harmful in high concentrations and it is especially problematic at pH levels above 7.0. In the second stage of the nitrogen cycle, bacteria called nitrosomonas oxidize the ammonia in the tank, thus eliminating it from the tank water. The byproduct of this process is nitrite which is just as toxic for aquarium fish as ammonia. In the third stage of the nitrogen cycle, bacteria called nitrobacter convert the nitrites into nitrates which are less harmful to aquarium fish but still toxic in high concentrations. The only way to remove nitrates from the tank, thus preventing a toxic concentration, is to perform weekly water changes.

Establishing the Nitrogen Cycle

When you first set up your aquarium it will take some time to establish a colony of beneficial bacteria sufficient to maintain the nitrogen cycle. Depending on the tank size and conditions, it generally takes one month or more for the nitrogen cycle to become fully established. The reason the nitrogen cycle is often referred to as “new tank syndrome” is because inexperienced aquarium hobbyists often  make the mistake of adding fish to their new tanks too quickly. Adding fish to a new tank before it has fully cycled can increase the biological load of the tank beyond the capacity of existing beneficial bacteria to handle – this can cause a number of problems including poor water quality and even the death of aquarium fish.

There are several ways to go about establishing the nitrogen cycle in your aquarium and there are also a few things you can do to speed the process along. One option is to add live bacteria cultures to your tank using substrate or filter media from an established tank. Another option is to install an EcoBio-Stone in your tank to introduce a colony of live beneficial bacteria that will jump start the biological processes in your tank. EcoBio-Stones are infused with live beneficial bacteria as well as the nutrients they need to multiply and maintain the nitrogen cycle in your tank. Once the nitrogen cycle has been established, the EcoBio-Stone will help to keep your tank water clean and clear for up to two years,  making your tank a healthier environment for your fish.