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Aquarium filter media, filtration methods – biological, chemical, mechanical

18 05, 2023

biological filtration

How biological filtration work?

What is biological filtration?

There are three main types of filtration: mechanical and chemical filtration are only an addition to biological filtration which is one of the most important elements for providing a healthy environment for fish and other animals in an aquarium. Biological filtration is the process involving nitrifying bacteria that boost the nitrogen cycle:

  • Nitrosomonas
  • Nitrospira

They transform harmful substances, such as ammonia and ammonium ions, into safer for fish nitrate ions, that can be removed from the water by:

  • Regular water changes.
  • The use of anaerobic bacteria that convert nitrate ions into molecular nitrogen

How to create proper conditions for beneficial bacteria in an aquarium?

When setting up the aquarium, it is essential to remember that the bacteria, like the rest of the organisms living in the aquarium, need proper living conditions. So, a little help from us will certainly help to boost beneficial bacteria population.

Best places for Nitrospira bacteria to grow:

  • Bio-pellets
  • Filter sponge
  • Filter floss (AF Filter Floss)
  • Ceramic rings (Perfect for both types of bacteria)
  • Substrates (AF Bio Sand)

Anaerobic areas for Nitrosomonas bacteria:

  • Ceramic rings
  • Volcanic rock

These elements should be taken into consideration when arranging an aquarium. We also recommend using biological filtration media, like Life Bio Fil, that is already settled with nitrifying bacteria. It is a type of biological filter which helps to accelerate the growth of bacteria and creates a friendly environment for the aquarium inhabitants.

Good to know

To make sure that the bacteria are starting to work, and it is possible to introduce animals into the aquarium, test the water and check the amount of nitrate, ammonia, and nitrite.

chemical filtration

Which chemical filter to use?

What is chemical filtration?

Chemical filtration is a type of filtration that can be used in addition to mechanical and biological filtration systems. It is not required, but certainly very helpful.

What are the advantages of chemical filtration?

One of the biggest advantages of using chemical filtration media is that we can remove many non-essential substances at the same time or, conversely, just one. It depends on the product we are using. For example: the use of Phosphate Minus significantly removes excess phosphate from the tank water. Zeo Mix effectively absorbs ammonia and ammonium ions.

Chemical filter media also allow us to:

  • Prevention of unpleasant odours
  • Reduce algae
  • Prevents water turbidity
  • Prevents water discoloration
  • Removal of residues of medicines used during fish treatment
  • Removal of heavy metals such as copper

Of course, we have to remember that the specific effect depends on the chemical filter media we are using.

Which is the best product for chemical filtration?

Unfortunately, there is no clear answer to this question. As we mentioned earlier, it all depends on the current situation inside an aquarium and what our goal is. However, we can tell you about the individual products. How they work and which substances they remove or reduce.

Active carbon

Active carbon is one of the most popular products used in these types of aquarium filtration. The carbon particles have hundreds of tiny pores that act as a trap for contaminants. It is worth noting that it works on a wide range of problems, removes:

  • Chlorine and chloramine
  • Dissolved proteins
  • Bad smells
  • Water discoloration


Like active carbon, it has hundreds of tiny pores, but it works in a different way. Zeolite absorbs ammonia and converts it into sodium. This process is called ion exchange. The main purpose of using zeolite is to remove:

  • ammonia


Chemical waste such as phosphate, heavy metals and nitrate can be removed from the aquarium using resin. The important thing when using resin is a filter bag to hold our medium. Because the resin is in small pieces, without this bag, it will float freely in the aquarium without any effect.

A way to get rid of phosphate

High phosphate and silicate levels should be reduced with Phosphate Minus. It's great for freshly established tanks, preventing excessive phosphate levels, and for older ones, lowering PO4 levels.

What should be kept in mind when using chemical filtration?

The most influential thing we need to mention is that none of these chemical carriers last forever. Sooner or later, they need to be replaced, otherwise, instead of absorbing pollutants, they may return to the aquarium, which is not what we want. This is why it is so important to keep a close eye on the aquarium and its parameters. Make sure you use filters with the correct instructions.

mechanical filtration

How mechanical filtration works in the aquarium?

What is mechanical filtration?

Mechanical filtration relies on mainly water flow through filter specific porosity. As with the previous filtration, mechanical filter media are only an addition to the aquarium. It is not the main type of filtration. These types of filters remove visual contaminants from the aquarium water, such as:

  • food and plant remains
  • fish waste
  • dust
  • cloudy water

Like other types of aquarium filters, this one also needs our attention. Any contaminants deposited on the filter can start a septic process, which can result in a nitrate spike.

Like other types of aquarium filters, this one also needs our attention. Any contaminants deposited on the filter can start a septic process, which can result in a nitrate spike.

Good to know

During cleaning filters, it is important to remember that the bacteria involved in biological filtration like to settle on the filter mechanisms. Using tap water or certain chemicals can remove much of it, resulting in an increase in ammonia and nitrite.

What is the difference between mechanical filters?

Mechanical filters are divided into:

  • Very coarse porous (best used as a mechanical pre-filter, so that filters with a lower porosity do not subsequently have to filter out large pieces of dirt).
  • Coarse porous (Similar as previous, this filter also can remove larger pieces of dirt).
  • Medium coarse porous (Thanks to this kind of filtration, you can observe slightly clearer water).
  • Fine filter (An ideal choice if you want clean water, combined with coarser filters to improve results).
  • Extra fine filter (This type of filtration provides the cleanest water. This filter can remove most contaminants. However, it is necessary to clean it frequently).

The lower the porosity of the filter, the finer the filtration. However, lower porosity filters fill up much faster, requiring cleaning.

Which type of filter in mechanical filtration is best for aquarium?

Unfortunately, there is no single correct answer. There are too many factors influencing the performance of mechanical filters to pick a winner:

  • Surface area and size of fish tank.
  • Type of filter used.
  • Water flow rate through the filter.
  • Mechanical filter size.
  • How often are we going to change/clean the filter, and how much time do we have for this?

What products to use for filters?

The most common types of aquarium filters: