3 types of aquarium filtration correspondingly use mechanical, chemical, and biological filter media as the key media to purify aquarium water. One of the filtration (mechanical, chemical, and biological filtration) has its respective mechanism but each had some bearing on the others (mechanical filtration reducing the load on biological filtration, chemical filtration dealing with what was left after biological filtration).

Mechanical aquarium Filtration and filter media

Mechanical filtration help remove of particulate matter from the aquarium water. Using mechanical filters can capture solid waste, reduce the load on biological filters, complement biological filtration and improve the visual clarity of the water. Some hobbyists prefer using skimmers to do this works than using mechanical filters. They are very effective in removing particulate matter and, in many ways, can take the place of mechanical filters.


A mechanical filter media (filter floss, ceramic pieces, foam or sponge filter media are common choices) can be used by packed in an internal or external canister filter. Beside, there are a couple of easy ways to do a mechanical medium by yourself. If your aquarium has a sump, you can run the water draining into the sump through a basket of filter floss or similar material or through a specially designed filter sock.

One key point when using mechanical filters is that they need frequent cleaning. If a mechanical filter is not cleaned regularly, the material it collects, with a constant stream of water running through it, will decay, and then the mechanical filter will increase the load on the biological filter rather than decrease it. Detritus left to decay in some quiet corner of the tank will release any nutrients that it contains very slowly. Take the same detritus, trap it on some filter media, and force oxygenated water through it, and it is likely to break down and release its nutrients much faster.

Biological Filtration and bio filter media, Bio Max

Aquatic animals (fish and invertebrates) excrete nitrogenous wastes, which is highly toxic in an aquarium; and biological filtration using living organisms such as bacteria, algae detoxify those wastes by converting them from ammonia to nitrite and then nitrate (a process called nitrification).

Briefly, biological filtration is the process of using living organisms (usually bacteria) to remove waste products, particularly nitrogenous compounds. The nitrification process is what classic biological filters are designed to do. They pump oxygen-rich aquarium water over substrates on which nitrifying bacteria can grow. Besides, the incoming water pre-filtered with mechanical filter media will provide nitrifying bacteria with clean and oxygen-rich surfaces that promote their activities.

Biological filter systems equipped with efficient biological filter media, such as Bio Max, provide these beneficial bacteria with the perfect environment.


This is the principle behind artificial biofilters ranging from simple sponge filters and undergravels, to biological media in canister filters and trickle filters, to fluidized sand beds. Such filters need to be cycled, or matured, prior to stocking the aquarium because the bacterial population needs to be large enough to handle the waste output of the first inhabitants.

This cycled or matured tank ready for stocking is usually done by adding a source of ammonia to the aquarium water and either waiting for bacteria in the environment to colonize the filter or adding a starter culture. Ammonia and nitrite levels are then monitored.

First ammonia levels drop and nitrite levels rise (as the bacterial population that converts ammonia to nitrite becomes established), then the nitrite level drops as another population of bacteria flourishes and converts the nitrite to nitrate. At the point where both ammonia and nitrite levels are zero, biofiltration is established and the process of stocking the aquarium can begin.

Chemical filtration and filter media, Fluval Carbon

Dissolved organic compounds can affect light transmission through water, giving it a yellowish tint; this can affect the growth and coloration of corals. Water changes also help to manage levels of dissolved organics, but to be most effective, a routine of regular water changes must be implemented from early in the tanks life.


Yellowish tint aquarium water

While biological filtration processes nitrogenous wastes very effectively, other types of waste products also accumulate in aquarium water. Skimming reduces levels of some dissolved organics but doesn’t remove all such substances.

Chemical filtration has important role in removing dissolved organics that remain after skimming, biological filtration and water changes. These include a wide range of dissolved organic compounds, some of which contain phosphates, which are major algae nutrients and can inhibit the growth of stony corals.

There are many types of chemical filter media that can be used to remove phosphates or nitrates. Carbon is probably the most widely used chemical medium for chemical filtration, as it adsorbs a wide range of dissolved substances. Fluval Carbon, a well-known chemical filter media can improve the clarity, color, odors of the aquarium water and effectively removes heavy metals.

Cacbon be used in a number of ways. If highly efficient chemical filtration is desired, carbon should have a strong flow of water through it. This can be achieved by placing it in an internal or external power filter or in a reactor fed with water by a pump. Another method is to place the carbon in a media bag and place this in a sump or a discreet place in the aquarium. Used in this way, the carbon has water flowing over it but not forced through it— this can be termed passive use of carbon.

Most other chemical filtration media (for example, phosphate removers) need to be used either in power filters or reactors with a strong flow of water through them to be effective. In some cases, fluidized reactors may be used to increase the efficiency of adsorption.

Unlike biological filtration, chemical filtration works by binding dissolved substances to media to remove them from the water: There is no chemical processing of those substances into less harmful compounds. This means that eventually the media will become saturated and will need to be replaced. While synthetic media that are saturated will usually simply stop adsorbing more waste products, carbon is more problematic in that when saturated, it can start to dump adsorbed substances back into the water. For this reason, it’s important to change carbon on a regular basis; somewhere between every month and every three months seems to work well.

Many hobbyists like to use carbon in two or more media bags within their systems so that part of the carbon can be changed at any one time. This reduces the possibility of a sudden large increase in the adsorption capacity in the system causing a rapid drop in dissolved organics, as could occur if all the carbon were changed at once.

One question that is worth asking about chemical filtration is whether your aquarium really needs it. If your tank has an efficient skimmer and you perform frequent partial water changes, the answer may well be no, particularly if the system is only lightly stocking.