Beneficial Bacteria of the Nitrogen Cycle in Aquariums Explained

The health of water bodies depends on the proper balance of beneficial bacteria that take part in what is called the nitrogen cycle. Because of the importance of the nitrogen cycle, aquarium enthusiasts and aquaculture specialists often purchase pre-made mixes of beneficial bacteria. Water “probiotics” ensure that harmful nitrogen compounds do not build up in the water and prevent what is called, “tank syndrome.”

Nitrogen Cycle Explained

Nitrogen is an essential element for any living thing as it is found in the major building blocks life: protein and DNA. Moreover, it is a main element in chlorophyll. Chlorophyll is the molecule used by plants for photosynthesis. In a nutshell, without nitrogen we couldn’t survive.

However, not all nitrogen compounds are the same. Nitrogen isn’t found in nature as single atoms. Instead, it comes in various forms such as ammonia (NH3), nitrite (NO2), nitrate (NO3), nitrous oxide (N2O), nitric oxide (NO) and nitrogen gas (N2). And, not all of these forms are harmless. Ammonia in water is deadly for fish and plants, which is why controlling this cycle in water is so important.

Tank syndrome is when fish mysteriously die after starting up a new aquarium. It is caused by the build-up of ammonia. Ammonia damages the gills of fish. However, the symptoms of this form of poisoning are various and include purple gills, clamped and damaged fins, gasping and inactivity. Unfortunately, once things get this bad, it’s very hard to save the fish. Another thing that ammonia does is encourage the growth of algae. Algae just love it. The best thing is to prevent the build up of ammonia in the first place by adding bacteria that can transform the harmful ammonia to less harmful nitrogen-containing molecules.

2008-08-22 White German Shepherd swimming in algaeSteps and Beneficial Bacteria of the Nitrogen Cycle

1. Decomposition

Ammonium is produced when organic matter decomposes, which is mainly the work of bacteria and fungi. In water, the organic material could be dead plants, dead fish, fish fecal matter and excess fish food. Normally, it doesn’t build up despite large amounts of decomposition, this is because of a set of bacteria called nitrifying bacteria.

2. Nitrification

Nitrification occurs when ammonia molecules are oxidized. This means simply that the nitrogen has offered some electrons to oxygen atoms and a new molecule is produced. The first product in this reaction is nitrite (NO2) and the second is nitrate (NO3). These products are harmless to fish and can be used by plants, algae and photo-synthetic bacteria to grow. Bacteria of the genera Nitrosamonas, Nitrosococcus, Nitrosospira and Nitrosolobus can convert ammonia to nitrite. Nitrite is converted to nitrate by the genera, Nitrobacter, Nitrococcus, Nitrospina and Nitrospira.

3. Dinitrification

Although, nitrite and nitrate aren’t that harmful, they can support blooms of algae if not removed. Removal is achieved by photo-synthetic bacteria. These bacteria, often called PSBs, use nitrogen molecules and light to grow. Unlike other bacteria, they contain bacteriochlorophyll. This gives them unique colors like blue-green and purple. In fact, blue-green algae are not algae at all. They’re actually PSBs. One of the most effective PSB species used in water bodies for dinitrification is Rhodopseudomonas plaustrus, a purple bacterium. These bacteria feed on the nitrogen molecules and produce nitrogen gas, which is then safely released into the atmosphere.

Steps of the nitrogen cycle in aquariums.
Steps of the nitrogen cycle in aquariums.

Adding Beneficial Bacteria to a New Aquarium

When starting a new aquarium, it really is essential to have these bacteria in place from the beginning in order to prevent the build up of ammonia. Stable populations of nitrifying and denitrifying bacteria take up to four weeks to develop if additional beneficial bacteria are not added. In this period, owners of new aquariums could rely on regular water changes to keep ammonia levels down. However, the option of buying a pre-prepared mix of beneficial bacteria would be safer and save tons of time.

Another problem that a new aquarium owner can encounter as a result of a poor nitrogen cycle is algae blooms. On the upside, algae will consume dangerous ammonia along with nitrites and nitrates. On the downside, it can completely take over a tank or pond if not controlled, which only encourages the release of more ammonia when algae die. The best defence and remedy is to make sure that you have good populations of nitrication and dinitrification bacteria in place so that excess nitrogen is released into the atmosphere.