Nitrifying bacteria are a group of autotrophic bacteria that use ammonia or nitrite as their primary energy source and carbon dioxide as their main carbon source. These bacteria are aerobic and can be classified into two types: ammonia-oxidizing bacteria and nitrite-oxidizing bacteria. Ammonia-oxidizing bacteria can convert ammonia nitrogen into nitrite, while nitrite-oxidizing bacteria can convert nitrite into nitrate.
Intensive aquaculture is today's most common method, with high stocking densities and short production cycles. Aquatic animals primarily rely on feed and fertilizers for nutrition. Consequently, aquaculture waters accumulate large amounts of organic matter, such as leftover feed, fertilizer, pharmaceuticals, animal excrement, and dead aquatic plants and animals. Heterotrophic bacteria break down proteins and nucleic acids in organic matter, producing ammonia and other nitrogenous compounds. Ammonia nitrogen can be converted into nitrite by ammonia-oxidizing bacteria or photosynthetic bacteria, which can then form nitrites by combining them with metal ions.
Ammonia nitrogen and nitrites are toxic to aquatic animals and significantly threaten the aquaculture industry.
Nitrification is an oxidation process carried out in stages by ammonia-oxidizing and nitrite-oxidizing bacteria. This process is most efficient under well-oxygenated conditions. Ammonia-oxidizing bacteria can oxidize ammonia to produce nitrite, while nitrite-oxidizing bacteria can oxidize nitrite to produce nitrate, a series of reactions collectively known as nitrification.
Nitrification can convert toxic ammonia nitrogen and nitrite into non-toxic nitrate, reducing the concentrations of ammonia nitrogen and nitrite in water, mitigating or eliminating their harmful effects on aquatic animals, purifying the water quality, and ensuring the healthy growth of aquaculture animals.
Do not use nitrifying bacteria simultaneously with disinfectants or bactericides to avoid killing the bacteria. If it is necessary to use bactericides or medications to treat fish diseases, wait at least one week after using the medication before introducing nitrifying bacteria.
The effectiveness of nitrifying bacteria is best when used under optimal temperature conditions. For example, photosynthetic bacteria can grow and reproduce normally within a range of 23-29°C. Below 23°C, their growth slows, and they become less effective.
Pay attention to changes in water pH during the use of nitrifying bacteria. For example, freshwater nitrifying bacteria work best at a neutral pH, while acidic conditions reduce their effectiveness. Adjusting the water in the aquarium to neutral or slightly alkaline conditions can enhance the effectiveness of the bacteria. Photosynthetic bacteria work best at a pH of 8.2-8.6, making them more suitable for saltwater aquariums.
Consider their compatibility when introducing different types of bacteria into the same environment. For example, nitrifying and photosynthetic bacteria should not be used in the same aquarium, as their water purification processes can inhibit each other and reduce their overall effectiveness.
Restricting bacteria to the aquarium alone may not provide enough space to reproduce, limiting their numbers and effectiveness. To address this issue, use a biofiltration system to create more living space for the bacteria, allowing them to proliferate and improve their ability to break down harmful substances.
Biofiltration systems are an effective method to introduce nitrifying bacteria into aquaculture systems. These systems use porous filter media to provide a large surface area for bacterial colonization. As water passes through the filter, bacteria break down ammonia and nitrite into less harmful substances, improving water quality and reducing toxicity to aquatic animals.
Regular monitoring of water quality parameters, such as ammonia, nitrite, nitrate, pH, and dissolved oxygen, is essential for ensuring the effective functioning of nitrifying bacteria. This monitoring can help identify potential issues and allow for adjustments to be made, such as altering the pH or temperature, to optimize the performance of the bacteria.
When introducing nitrifying bacteria into a new aquaculture system, it is essential to acclimate them properly. Gradually introduce the bacteria to the new environment to prevent shock, which could decrease their effectiveness. Additionally, avoid overloading the system with too many new organisms at once, as this could lead to an imbalance in water quality and stress the nitrifying bacteria.
Overstocking aquaculture systems can lead to excess organic waste, overwhelming the nitrifying bacteria and making it difficult for them to maintain water quality. It is essential to keep proper stocking densities to avoid overloading the system and ensure that the bacteria can effectively process waste products.
Regular maintenance of the aquaculture system, including cleaning the biofiltration media and removing excess organic matter, can help maintain optimal conditions for nitrifying bacteria. This maintenance helps prevent the buildup of harmful substances and ensures the continued effectiveness of the bacteria in preserving water quality.
Nitrifying bacteria play a critical role in aquaculture by converting toxic ammonia and nitrite into less harmful substances. Proper implementation and management of nitrifying bacteria in aquaculture systems can help maintain water quality, reduce the risk of disease, and promote the healthy growth of aquatic animals.