All about Aquarium Filtration

A fish tank is a closed system. Your pet fish will live in the same amount of water until you change the water. (Imagine what would happen if you were put in a covered room and given only food). The main purpose of the filter is to keep the water quality of the fish tank in a favorable condition for the fish until you change the water, which removes excess food, decomposing organic matter, free floating particles, hazardous chemicals and fish waste.

Here water purification should be done in 3 main ways.

  1. Mechanical Filtration
  2. Biological Filtration
  3. Chemical Filtration


Mechanical Filtration

Mechanical filtration, also known as mechanical filtration, is provided by passing water through a filter. The most commonly used sponge for this is the one made for the aquarium. As water passes through the sponge, all the impurities that could not pass through it are deposited on the sponge.

Here you need to use a high density sponge to increase the quality of the filter. But keep in mind that cleaning a sponge in a very short period of time is mandatory as the amount of waste that accumulates when using a high density sponge is higher.


Biological Filtration

Biological filtration is the most important stage of all. Most of the pet fish in the aquarium hobby die due to not getting the required filtration properly at this stage. To understand biological filtration you need to understand the basic process of an aquarium. This process is called the nitrogen cycle.


Nitrogen Cycle

Add ammonia to the water in your aquarium from fish waste, decaying plant parts and uneaten fish food. Increasing the ammonia composition of the water is highly toxic to fish. In nature, there is a species of bacteria called “nitrogen-fixing bacteria” that can prevent this condition. This bacterium converts the ammonia composition of water into nitrite.

Nitrites are responsible for the death of pets in the aquarium hobby. Nature has created a species of bacteria called “nitrite-loving bacteria” to prevent this condition. Nitrites, which are very harmful to fish, are converted to nitrate by “nitrite-loving bacteria”. Although nitrate is relatively harmless to fish, it can be harmful to fish if the nitrate content of the water is too high.


Aquarium Bio Media

As mentioned above, the “nitrogen-fixing bacteria” and “nitrite-loving bacteria” created by nature are essential to live in your aquarium, converting the ammonia in the water to nitrate, which is not harmful to fish, and maintaining the balance of the water. We need to create a medium for these bacteria to live easily. Even if the bacteria live to some extent on the sand, rocks, and twigs in your aquarium, you need to add to your filter the mediums created for this process, called bio media, to increase the efficiency of the nitrogen cycle.

Most commonly used media for this are Ceramic Rings, Bio Balls, K1 Media.

This Bio-Media is designed to have a large surface area in a small space. This allows a large number of bacteria, which are essential for the Nitrogen Cycle, to live in a small space.



  • Apply only the amount of Ammonia produced in your Fish Tank to the Bio-Media Filter. Even if a large amount of Bio-Media is added to your filter, it does not mean that it will be a very good filtration. Understand the size of your pet fish, the amount of food you eat and the amount of waste produced by a fish tank and add as much bio-media as you need.
  • Never allow Bio-Media to dry while cleaning the filter. The bacteria that live inside cannot survive without water.
  • Use a very good mechanical filtration before biological filtration. If the waste produced by the aquarium is deposited in the bio-media, the required process will not take place properly.
  • Never clean Bio-Media with chlorinated water. Chlorine destroys the beneficial bacteria in it. The water in the fish tank is best suited for bio-media purification.

produced Nitrate can only be removed by changing the water in the FISH tank, applying live aqua plants to the aquarium itself, or using a medium such as Purigen.


Chemical Filtration

As the name implies, this stage involves the removal of harmful chemicals dissolved in water. In addition, ammonia, nitrite, and nitrate are eliminated

  • Removal of heavy metals such as copper.
  • Removal of compounds such as sodium chloride.
  • To eliminate water staining.
  • Used to eliminate odors from aquariums for a variety of reasons.

Simply, chemical filtration can be used to remove any harmful compound that cannot be removed by mechanical and biological filtration. The following mediums are used for this purpose and the required chemical filtration can be obtained by allowing water to pass through these substances.


Activated carbon

The main medium used for chemical filtration is activated carbon. Also known as activated carbon, this is the most commonly used chemical filter medium. A big reason for the popularity of activated carbon is that it can deal with a variety of pollutants and is readily available at an affordable price. Millions of tiny holes are formed in a piece of activated carbon. These holes are so small that you cannot see them with the naked eye. These tiny holes retain harmful chemicals dissolved in the water and purify the water.

Activated carbon activates chlorine and chloramine, dissolved proteins in water, which can degrade water and eliminate water odor.

In addition, the following materials are used sparingly.


Zeolite mainly removes ammonia


Oxide removes phosphates dissolved in water.


There are resin variants that are made for a variety of purposes and are used to remove impurities such as phosphate, nitrate and heavy metals.


  • Chemical filter media have a specific shelf life. This time varies for different mediums and also depends on the nature of your aquarium. At the end of this time a new medium must be added as this does not make any difference to the water.
  • If drugs are being added to your aquarium for any medical condition, the chemical filter media should be removed. Otherwise all the medicine you collect will be absorbed by the filter media.