Why do our aquariums need fish tank filtration? This is because there is often a significant disparity between the biodiversity and water volume in natural environments and those in aquariums. Natural bodies of water boast rich biodiversity, including various microorganisms, plants, and animals that work together to purify the water. When animals and plants die, decomposers break them down, and the nutrients released are reabsorbed by plants, forming a complete cycle of matter. Additionally, natural water bodies are typically large, and currents help dilute waste and harmful substances. In artificial environments like aquariums, however, biodiversity is limited, and the volume of water is relatively small, making it easy for waste concentrations to rise. Therefore, filters are needed to help remove waste and harmful substances.
Why do fish suddenly die? Why does the water in the aquarium become cloudy? To answer these questions, we must mention the harmful substances that can accumulate in aquariums and the dangers they pose. If you’re not interested in these details and just want to solve the problem of dead fish, you can skip to the solution here-fish tank filtration
The Hazards of Ammonia, Nitrite, and Nitrate
Ammonia, nitrite, and nitrate are produced when fish excrement, leftover food, and plant debris decompose. This is one of the main reasons for water quality deterioration. Ammonia is a toxic substance that has a direct toxic effect on aquatic life. It can directly affect the gill tissue of fish, causing breathing difficulties. Fish exposed to high concentrations of ammonia over a long period may experience reduced appetite, slow growth, and even death. Ammonia in the water is converted into nitrite by nitrifying bacteria with the help of oxygen. Nitrite binds with hemoglobin to form methemoglobin, which impairs the blood’s ability to transport oxygen. Fish exposed to high concentrations of nitrite over time may develop anemia and asphyxia. Next, nitrite is further oxidized into nitrate by nitrobacteria. While nitrate is relatively stable and less toxic, if it accumulates excessively, it can still have adverse effects on the fish and water quality in the aquarium. High nitrate levels can impede fish growth and reduce their immune system function. Moreover, nitrate is an important nutrient source for algae growth. Excessively high nitrate content can lead to overgrowth of algae.
In general
Ammonia, nitrite and nitrates produced by the decomposition of fish waste, leftover food and plant debris are the main causes of water quality deterioration.
- Ammonia is toxic to aquatic organisms. It can affect the gill tissue of fish and cause breathing difficulties. Long-term exposure may lead to the death of fish.
- Ammonia is converted into nitrite under the action of oxygen and nitrite bacteria. Nitrite will damage the blood’s ability to transport oxygen, causing anemia and suffocation in fish.
- Nitrite is converted into nitrate by nitrate bacteria. Although it is less toxic, excessive accumulation will still hinder the growth of fish, reduce its immune system function, and promote excessive growth of algae.
Introduction to fish tank filtration system
Having discussed the potentially harmful substances that can exist in aquariums and their hazards, let’s explore how aquarium filtration works. Modern aquarium filtration systems typically consist of three types of filtration: physical, chemical, and biological. Let’s take a closer look at the filtration process:
1. Pump Startup and Water Extraction
The pump in an aquarium is like a tireless “water sprite,” tirelessly working to draw up water from the bottom of the tank. This water carries the metabolic products of the fish, uneaten food, plant debris, and tiny suspended particles, beginning its journey of purification. The humming of the pump is like the prelude to this purification ritual, signaling the start of the journey.
2. Physical Filtration: Initial Screening and Interception
As the water is pumped into the filtration system, it first encounters the first line of defense – the physical filtration layer. This layer is usually made up of multiple layers of filter wool, acting like a “filter net” or “air purifier” in a city. Large particulate matter, such as fish feces, leftover food, and plant debris, is caught by the fibers of the filter wool, unable to proceed further. These impurities gradually accumulate on the filter wool, forming layers of “dirt,” while the clear water passes through this “filter net” and continues on to the next stage.
3. Chemical Filtration: Assistance and Regulation
Some aquarium filtration systems also include a chemical filtration layer. This layer typically uses materials such as activated carbon and water softening resins, which can further remove odors, pigments, and some dissolved harmful substances from the water. These materials act like an upgraded version of “clean-up crews” in the water, using their chemical properties to “intimately interact” with harmful substances in the water, firmly adsorbing them onto their surfaces. Thus, the water becomes purer and fresher as it passes through this layer. Of course, the adsorption capacity of these compounds is limited, so they should be replaced promptly.
4. Biological Filtration: The Magic of Nitrifying Bacteria
After passing through physical filtration, the water enters the biological filtration area. This type of filtration is the most important for maintaining fish in an aquarium. Here, nitrosomonas and nitrobacteria have their “home.” Nitrosomonas converts ammonia into nitrite. Establishing a healthy colony of nitrosomonas takes about 2-3 weeks, and the bacteria require oxygen for reproduction. Providing a survival medium (such as quartz balls) and water with sufficient oxygen will cause the bacterial population to grow explosively. Once established in the filter media, these bacteria immediately convert all available ammonia in the water into nitrite.
However, nitrite is also a dangerous compound for fish health. At this point, nitrobacteria are needed to convert nitrite into nitrate. Nitrobacteria take approximately 2 weeks to establish a healthy colony. Therefore, establishing a colony of digestive bacteria in an aquarium takes around 4-6 weeks. Once established, the bacterial colony will continue to reproduce on its own, living off the fish’s excretions and organic matter.
These bacteria initially grow explosively, leading to what is known as a bacterial bloom. A large number of bacteria in the aquarium can make the water appear cloudy. This is a normal part of cultivating nitrifying bacteria. Once enough nitrifying bacteria fill the bacterial house, excess bacteria will die off, and the water in the aquarium will become clear. This process typically takes a few days. Finally, fish kept in water with high nitrate levels can face various health issues, so it is common to plant aquatic plants in the aquarium to absorb nitrate.
5. Return and Recirculation
After passing through physical, biological, and chemical filtration, the water returns to the aquarium. The water has become clear and transparent, rich in oxygen and beneficial microbial communities, providing a healthy and comfortable living environment for the fish. Meanwhile, the pump continues to work, drawing up water from the bottom of the tank again to begin another round of purification. This process repeats itself, continuously maintaining the stability and balance of water quality in the aquarium.
Aquarium Water Changes
When changing the water, it is not recommended to replace all of it with new water but rather only 10-15%. For larger aquariums, up to 20% of the water can be changed each time. The old water removed can be used to rinse parts of the filter containing nitrifying bacteria. Remember not to use tap water or chlorinated water to clean the filter, as chlorine can kill nitrifying bacteria.
Through the above content, we have gained some understanding of aquarium filtration. In the next article, we will look at excellent aquariums and fish tank filtration.
