What Is A Biofilter For An Aquarium And Why It Is Needed How To Do It Yourself

The life of the inhabitants of the aquarium is directly dependent on the quality of water in the tank.

Without a good filter, the water becomes turbid and unsuitable for underwater inhabitants.

In this article we will consider the biofilters, analyze their advantages and disadvantages, and also tell you how to make it yourself. In addition, we consider the purchase models of such filters for your aquariums.

What it is?

Biofiltration implies the mandatory participation of living microorganisms in the process of improving the quality of the aquatic environment. Ammonia, which is released during the life of fish, adversely affects them. One of the ways to get rid of this substance is to replace water, however, it will be more efficient to run nitrifying bacteria into the reservoir.

Any aquarium can be classified as a biofilter. filter that circulates the fluid through the bacteria substrate. In order to ensure the circulation of water will be enough simple pump.

Bacteria can be colonized on any substrate, for example, on plants, walls of an aquarium or soil. However, bacteria need oxygen for vital activity, so they settle in a small layer, which may be insufficient in case of a small aquarium area.

The density of planting fish in the tank exceeds a thousand times their density in their natural environment, the same applies to nitrifying bacteria.

Advantages and disadvantages

The advantages of using a biofilter include the following factors:

  • Biofilter makes aquarium hygiene much easier, which saves time on care. You no longer have to worry about disposing of the remains of rotting plants, fish excrement, remnants of food.
  • Biological filter does not affect chemical processes., occurring in an aquarium after it has established a biological balance. The biological filter only contributes to the stabilization of this equilibrium and makes the flow of regular processes in the aquarium more intense.
  • Biofilter cost is not high, besides, you can do it yourself at home.

The disadvantages of biofilter include reducing the effective height of the aquarium, which can adversely affect the plants. Also, if you use a sponge as a biofilter, it can quickly become dirty.

Why do you need?

Bacteria are not a drug that can be poured into the tank from the bottle. They are initially present in the aquarium, on its walls, decorative elements, and so on.

Reproduction in microorganisms occurs very quickly, so you only need to create a comfortable habitat for them.

It is for this purpose that a biological filter is used, which is filled with various materials used to increase the contact surface and ensure the reproduction of microorganisms).

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Operating principle

In this filter, all the work is carried out by the bacteria in it. Therefore, the filler itself, until microorganisms settle it, performs only mechanical purification of water, collecting small dirt. Bacteria that perform cleaning functions can be of two varieties:

  • Nitrifying bacteria (Ammonia is oxidized to hydroxylamine, and then to nitrite and nitrate).
  • Nitrobacteria (They feed on nitrites, and then transform them into nitrates).

Thus, it can be concluded that the principle of operation of all biological filters is based on creating comfortable conditions for bacteria, which will split ammonia dangerous for fish and help establish perfect biological equilibrium in the reservoir.

Fillers for aquarium biological filter

Quality filler will contribute to the proliferation of bacteria in the aquarium. Below we take a closer look at each of the types of biofilter fillers, and also give their advantages and disadvantages.

Foam rubber

What Is A Biofilter For An Aquarium And Why It Is Needed How To Do It Yourself

This is the most common material for biofilters. Its advantages include the fact that it is not so often clogged, in contrast to the padding polyester, as well as a large area for the colonization of bacteria.

Among the minuses you need to highlight the fact that the sponge clogs quickly enough, which can lead to deterioration of water filtration in the aquarium.


The porous structure of ceramic rings promotes reproduction and development of beneficial bacteria. It is not necessary to wash the bioceramics, only rinse occasionally in an aquarium liquid. Among the advantages of such a filler, its durability is worth noting (high-quality ceramics last up to five years). The disadvantages include the relative high cost (good stuff costs more than five hundred rubles).


Glass filter filler is one of the latest developments in aquariums. Experts believe that such a filler is by far the best. In the process of incandescent glass, millions of microscopic holes are formed in it, into which bacteria are colonized.. The service life of such a biofilter is more than five years. Minus – the high cost.

Special plastic

Special balls are made of plastic, on the surface of which there are notches. Among the advantages can be noted durability, as well as the fact that when passing through such a filter, the active saturation of the liquid with oxygen occurs. On the other hand, if poor quality plastic was used for the manufacture of the filler, this can lead to an imbalance of the biological balance in the aquarium.

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Sintepon is used to improve the mechanical cleaning of the fluid in the tank. It has a high density, so it retains even the smallest particles of dirt at the entrance. If a padding pad is placed in your filter, then in a couple of hours after cleaning the aquarium, this filter material is able to trap almost all the dust and turbidity that has risen after cleaning with the help of a siphon of aquarium soil or grass weeding.

The main disadvantage of the padding polyester is that it pollutes very quickly. Such a filler needs to be changed every week, otherwise it will lose all sorbing properties. Due to its impracticality, the synthetic winterizer can be used as an emergency tool when you need to clean the aquarium from mechanical suspensions.


As for the use of zeolite in the aquarium, serious discussions flare up.

Some consider it an "absolute evil", completely unsuitable for use in the artificial underwater world, while others express the opinion that it is the best filter filler.

Among the advantages of this substance are:

  • Removal of drugs from water;
  • Use as a primer for plants;
  • Low cost.

The disadvantage of zeolite, as a biological filter, is a small pore diameter, which is not sufficient for the reproduction of beneficial bacteria.

Expanded clay

Not the best choice for filler. It has a small area for colonization of bacteria (25-400 square meters per liter, and ceramics has 600-1400 square meters per liter), and it can also contain phosphates, silicones and heavy metals, which are harmful to the biological balance of the aquarium. The only the advantage of using this material is its low cost.

How to do biological filtering with your own hands?

Below we look at several ways to make a homemade biofilter at home.

Simple option

  • For the manufacture of the simplest biofilter you need a glass jar with a volume of less than one liter. It must be tightly closed with a plastic cap, in which you need to make holes for the pipe and several small holes, so that water can flow into it.
  • From another cover, make a partition and place filtering material on it. A simple homemade filter is ready. Alternatively you can use a ceramic vessel.

A little more difficult

Slightly more difficult option would be to make a biological filter from a plastic box.

Do-it-yourself video about making the filter

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What to look for when buying?

Choosing a filter should be based on three criteria: the dimensions of the tank, which plants and fish live in it, as well as the possibilities of your budget.

Also pay attention to filter performance and the possibility of installing several fillers in it at once.

When choosing a substrate, give preference to a ceramic or glass filler, and if you want to save money, then buy a sponge. Or purchase several fillers at once, if your filter allows it.

Top 3 manufacturers

Below we give several options for manufacturers of biofilters for the aquarium.

DENNERLE Scaper’s Flow

Among the mounted biofilters are Scaper’s Flow. This model is very convenient, as its design allows its use not only as an external filter, but also as an internal one. This filter is relatively inexpensive and easy to maintain.. The downside is that this device is suitable only for small aquariums.

JBL CristalProfi

The internal CristalProfi filter is suitable for both mechanical and biological filtration. There are several varieties of this model for different volumes of tanks. It is equipped with a pump that drives water through a porous sponge that collects debris and bacteria. The disadvantage of this filter is that the sponge needs to be cleaned at least once every two weeks.

A water filter that is suitable for aquarists. The Japanese model has a large capacity, but it is quite expensive.

How to contain?

Care for such a cleaner, of course, is needed. However, at one time only a part of the filtering material should be cleaned or replaced. Maximum – one third of all material inside. But This filter cannot be completely cleaned, since you will destroy the beneficial bacteria in it.. Therefore, for a few weeks your tank will be left without biological protection, which can lead to the worst consequences.

Are there alternatives?

As an alternative, the role of a biofilter can be played by algae, which are collected in a separate vessel, where aquarium water is taken in through a mechanical filter.

Also alternative may serve as a dense settlement of the aquarium various plants. They absorb ammonia from water no worse than bacteria.

The main task of an aquarist is to create a biological equilibrium in which all inhabitants of the aquarium will live comfortably. This can help biofilter with the correct content. Now you know not only which substrate to use as a “filling”, but also how to make a filter with your own hands.