Bacteria in the aquarium - how it is related
The aquarium is a complex and dynamic ecosystem. Bacteria in this ecosystem play a key role, influencing water quality, the nutrient cycle, and the overall health of the aquarium. This article explores the invisible world of these microorganisms and their impact on life in the aquarium.
Bacteria in the leading role
All bacteria are aquatic in the sense that they reproduce and feed in water. Even bacteria in dry soils live in microscopic "pore water" within the soil. Some bacteria live freely in the water, but most attach to surfaces such as rocks, glass, etc. Bacteria often live in biofilms, which are complex, well-organized communities of other bacteria, algae, and protozoa.
Initial colonization – attachment to a surface by just a few microbes – gradually develops into a biofilm, a kind of 'microbial city.' Microbes in biofilms work together, exchanging nutrients, waste products, and genetic material.(1)
The role of bacteria in aquariums
The nitrogen cycle
- Ammonia production: The cycle begins with fish and other organisms producing waste that decomposes and releases ammonia. This substance is toxic and can be fatal to fish even in small concentrations.
- Oxidation of ammonia: Beneficial bacteria that live in the aquarium filter and on other surfaces (such as substrates and decorations) convert ammonia into nitrite. This is the first stage of nitrification. These bacteria are known as Nitrosomonas. The resulting nitrites are also toxic, but less so than ammonia.
- Nitrite oxidation: another group of beneficial bacteria, called Nitrobacter, take over and convert nitrites into nitrates. Nitrates are much less toxic than nitrite and ammonia, and most fish can tolerate them in higher concentrations
Nitrification is a process where microorganisms (bacteria and archaea) convert toxic ammonia into non-toxic nitrates. In new aquariums, nitrifying microbes gradually colonize aquarium filters, where they have enough surfaces to attach and oxygen to thrive. Although nitrifying bacteria play a secondary role in natural ecosystems, they are found in all soils, sediments, and natural waters.(2)
Reduction of nitrates: In properly maintained aquariums, nitrates can be removed by water changes or absorbed by plants. In more advanced systems, anaerobic bacteria can convert nitrates into nitrogen gas, which then escapes into the air. This process usually requires specific conditions not present in all aquariums.
Decomposition
Bacteria break down organic matter—dead plants, uneaten food, and fish waste—preventing the accumulation of harmful substances. This process also releases nutrients back into the water, which can be used by plants and other microorganisms.
The most important bacterial process in a planted aquarium is the decomposition of organic matter. Without this slow and continuous recycling process, organic matter (e.g., fish waste, dead plant leaves, fish food) would simply accumulate at the bottom of the tank.
Decomposition benefits aquariums in three main ways. First, it supplies plants with CO2 and other nutrients. While these nutrients can be artificially added to stimulate plant growth, bacterial decomposition provides them naturally. Fertilizing plants – by feeding fish – occurs continuously, in small doses, and with minimal effort. Second, dissolved organic carbon from decomposition keeps micronutrients in solution and available to plants. Without dissolved organic carbon in the water and sediment, important nutrients like iron and manganese would form insoluble oxides and become unavailable to plants. For floating plants without roots accessing substrate iron, this method of delivering iron is crucial. Third, dissolved organic carbon protects fish and shrimp from metal toxicity and acidity.(2)
Prevention of diseases in the aquarium
Beneficial bacteria can compete with harmful pathogens for resources, effectively suppressing diseases. Some bacteria also produce substances toxic to pathogens, further protecting aquarium inhabitants.
Types of beneficial bacteria
Aerobic bacteria in the aquarium
These bacteria require oxygen to function and are key to the initial stages of the nitrogen cycle. They are found on surfaces exposed to the water column, such as gravel, filter media, and decorations.
Anaerobic bacteria in the aquarium
Found in environments with low oxygen, such as deep substrates or inside dense filter media, these bacteria can perform denitrification, a process that reduces nitrate levels and prevents harmful concentrations.
Facultative bacteria in the aquarium
These bacteria can function in both aerobic and anaerobic conditions, making them highly versatile. They play a role in reducing excess nutrients and stabilizing environmental conditions in the tank.
Bacteria in aquariums
The aquarium cycle
To establish a stable community of beneficial bacteria, new aquariums must go through a process called "cycling." This involves introducing ammonia sources to the tank and allowing bacteria to form colonies capable of handling the biological load of the tank. The cycle is complete when ammonia and nitrite levels are undetectable, and nitrate levels stabilize.
Regular maintenance
Regular water changes not only control nitrate levels but also remove excess nutrients that could lead to bacterial "blooms." Cleaning filters, substrates, and tank walls helps prevent detritus buildup and maintains the optimal health of bacteria.
Monitoring water parameters
Regularly testing water for ammonia, nitrite, and nitrate helps aquarists adjust their routines and feeding to ensure a healthy bacterial balance and overall tank stability.
Other topics
Microbial balance in the aquarium
Achieving a balance between different microbial communities is crucial. Uncontrolled, some bacteria may dominate others, leading to poor water quality and unhealthy conditions for aquatic life.
Explosive bacterial growth
Aquarists can use supplements to boost bacterial efficiency or introduce new strains that improve nutrient absorption, filtration technologies, or enhance ecosystem resilience.
Dangers associated with bacteria in the aquarium
Not all bacteria are beneficial; some can cause diseases. Identifying and controlling these pathogens through quarantine practices and careful monitoring of water quality is essential. Sudden increases in nutrients or organic matter can cause explosive bacterial growth. For example, if the power goes out and the external filter stops, harmful bacteria can multiply in the filter, leading to anaerobic biofilm activity. Bacteria in the filter may suffocate and die. Once power is restored, toxic material from dead and decaying microbes can be released into the water.
It's recommended to monitor fish, and if in the morning, when oxygen levels are at their lowest, fish show signs of labored breathing or lethargy, it's an indicator that the water is insufficiently aerated.
For aquarists, ensuring sufficient oxygen for the tank's ecosystem is crucial. There are many ways to balance O2 consumption by fish and bacteria with O2 input from photosynthesis, air diffusion, and mechanical mixing of air with water.(4)
Conclusion
Understanding and balancing the environment, including bacteria, is the foundation for maintaining a healthy aquarium. With the right knowledge and tools, aquarists can harness the power of bacteria to create a thriving aquatic environment.
(1)Walstad, Diana . Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise (p. 99). Echinodorus Publishing. Kindle Edition.
(2)Walstad, Diana . Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise (p. 87). Echinodorus Publishing. Kindle Edition.
(3) Walstad, Diana . Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise (p. 105). Echinodorus Publishing. Kindle Edition.
(4) Walstad, Diana . Ekologie akvária s rostlinami: Praktická příručka a vědecké pojednání (str. 109). Nakladatelství Echinodorus. Vydání pro Kindle.
