How To Choose The Right Fish Tank Filter

Choosing the right filtration system for your aquarium is an important decision that will affect not only the types and number of people, but also the amount of maintenance the aquarium has to maintain the system. The filtration system helps keep the water clean, free from particulate matter (tiny fragments of plant materials, food debris, feces, fish waste, etc.) and toxic compounds that are dangerous to residents. This article will discuss the strengths and weaknesses of commonly available types of Fish Tank Filters so that you can make the right decision when choosing equipment for your aquarium.

There are three types of filtration that are necessary to maintain the health of any aquarium:

Before choosing an Fish Tank Filter, you should understand how all three types of filtering work for the benefit of your aquarium.

Filtration types

Mechanical filtration

Mechanical filtration is the process of removing solids from water. To do this, the aquarium water is driven through some substance (material), in order to catch and hold these tiny particles. The filtering material can be represented by a variety of forms: fibrous filaments, sponges of foam rubber or padding polyester, compressed paper or infusor earth, gravel. For proper operation, it is important that the filtering material regularly purifies the water, holding solid particles to their complete decomposition and release of decay products back into the aquarium.

A very common misconception of aquarists is that the more powerful the filter in the aquarium, the more fish can be kept in the system, and the filter requires less maintenance. All filters with mechanical filtration will eventually become clogged with particulate matter. When the filter is heavily clogged, this leads either to a decrease in the flow of water through it, or it will cause the water to move around the filter material. In this case, the filter must be cleaned. The filter can become completely clogged within a month, which means that the filter should be cleaned from clogging at least once a month. Even if the aquarium appears to be completely free from particulate matter, the filter will constantly emit a large amount of decomposition products (tiny particles of decomposition of plants and animal materials) and other debris that will slowly rot, contaminating the water with toxic decomposition products such as ammonia, nitrite and nitrates. This waste will actually lead to a reduction in the population of the aquarium.

Chemical filtration

Chemical filtration removes toxic or unwanted chemicals by passing water through the filter media. Recently, many advances have been made in this area, as a result of which new filtering agents have emerged that are focused on the elimination of specific chemicals or excess nutrients from water. These products can be added to the filtration system and, if used properly, will help to improve the quality of the water, as well as reduce the number of water changes needed to maintain a healthy aquarium. However, it should be remembered that during chemical filtration it is necessary to control the chemical composition of water and, if necessary, make water changes. Usually, activated carbon is used for chemical filtration.

Biological filtration

In biological filtration, various types of bacteria convert toxic chemical waste products of aquarium inhabitants into less toxic nutrients. This bacteriological processing process is called the nitrogen cycle.

Let’s look at how it goes nitrogen cycle. As a result of the processing by bacteria and fungi of waste products from fish, plants and invertebrates, as well as dead organisms and feed debris, ammonia is formed. Ammonia is extremely toxic to all inhabitants of the aquarium. Ammonia is converted to nitrites using nitrifying aerobic bacteria from the genus Nitrosomonas. Although nitrites are not as toxic as ammonia, even at low concentrations they are still harmful to fish and invertebrates. Other aerobic bacteria Nitrobacter, acting also as Nitrosomonas, substantially convert nitrites and convert them to harmless nitrates. At low and moderate concentrations, nitrates do not harm most fish and invertebrates, but their excess can cause the appearance of algae and their excessive growth, if you do not make regular water changes or do not use chemical filtration.

The diagram shows the nitrogen cycle.

In order for the nitrogen cycle to work properly in an aquarium, there must be a sufficient area for growth in a sufficient number of bacteria necessary for the nitrogen cycle. Also, aerobic bacteria need oxygen for growth and proper functioning, so their need for it must be replenished.

Biological filtration to some extent occurs in an aquarium wherever necessary bacteria can be found: in all filters, on all surfaces, in water, in the ground and on decorations. The capacity of a biological filter is determined by the available surface area for the growth of bacteria and the oxygen content of the water passing through it. Not all filters have the same features when it comes to biological filtration. Filters in which the filtering substance passes air better will have the greatest power.

Fish Tank Filters. Types

There are many Fish Tank Filters on sale now that differ in size, price and ability to perform three basic types of filtration. There are such filters:

  • internal airlift
  • bottom
  • external power (mounted)
  • canister internal
  • wet-dry exterior
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Before you purchase an Fish Tank Filter, decide who and what will inhabit your aquarium. For example, a freshwater aquarium with live aquarium plants usually does not require a filter with active biological filtration, but requires effective chemical and mechanical filtration. And in an aquarium without live plants, densely populated by African cichlids, you need a filter, or a combination of filters, in which all three types of filtration will be effective. Below we consider the existing available filters and their ability to perform all three types of filtering, their price range and care for them. At the end of the article is a summary of the table.

Internal airlift filters

Internal airlift filters are of different types: there are those that are installed in the aquarium directly to the bottom or the ground, other suction cups are attached to the wall of the aquarium. Such filters have an air supply line that is connected at the inlet and driven by an air pump that is located outside the aquarium. Air is pumped in the lower part of the filter, passes through the filtering material and is thrown out to the outside in the upper part of the filter, where it is scattered over the surface of the water. The action of air bubbles creates the movement of water through the filter, which allows it to perform filtration.

Corner Box Filter. As a rule, such a filter is made in the shape of a box so that it fits into the corner of the aquarium. It’s just a box with slots in the top and bottom that allow water to pass through it freely. Air is supplied to the lower part of the filter by means of a pump (compressor) installed on the surface outside the aquarium. Air pushes water through the filter from below and pushes it out at the top of the filter.

The corner filter performs all three types of filtration, but the effectiveness of all three types is limited due to the low oxygen content and low water flow. As a filtering material for mechanical and chemical filtration, a sponge and activated carbon are usually used for these types of filters, but other mechanical and chemical materials are also possible. Bacteria growing on the filter material provide biological filtration.

Such a filter should be washed / replaced depending on the load of the aquarium. And take care not to destroy the biological environment that has multiplied on the sponge. To do this, it is better to rinse it in water, which was drained from the aquarium during the substitution, and not under running tap water. And in no case can you boil a sponge or process it with hot water!

Sponge model. U-shaped model in which air with water passes through a sponge with a large surface area. A separate pump (compressor) is required to provide air flow.

The sponge material is capable of mechanical and biological filtration. The sponge retains solid particles from the water passing through it, thereby performing mechanical filtration. Biological filtration is performed by beneficial bacteria living on the sponge. The mechanical and biological functions of such a filter are limited, due to the small flow of air and water passing through the sponge.

Airlift filters very cheap and easy to maintain. It is enough to rinse the filter material once a week, cleaning it from organic matter before they start to spoil the water. Using aquarium water to clean the filter material is very important so as not to kill the beneficial bacteria involved in biological filtration.

Both types of internal airlift filters are of limited use, they are effective only in small aquariums with a small number of people. Most often, this type of filter is used in aquariums for fry or for quarantine aquariums. Since there is no movement of the water flow, it prevents the newly hatched fry from being sucked into the filter, which reduces their mortality. In a quarantine aquarium, such a filter is placed in order to pre-populate it with beneficial bacteria. In addition, the lack of water flow reduces the additional burden on sick fish. Well, again, these filters are inexpensive and very easy to use.

Bottom filters (under the ground)

For the bottom filter, a slit plate is used that is installed under the substrate (under gravel, for example) and has several tubes, called lifting tubes, which extend up to the surface of the water.

Mechanical filtration occurs when water flows through the substrate, which traps all the solid particles. It is very important every week to siphon ("vacuum" the hose) the soil, removing solids before they begin to decompose.

Biological filtration is carried out with the help of bacteria living on a large surface area of ​​the substrate through which water passes. However, biological filtration is limited due to the low oxygen content of the water passing through the gravel. In addition, the level of biological filtration falls even because water does not flow evenly through the soil because of its different levels and because of the decorations located on it. This creates dead spots inside the filter bed. Detritus accumulates in these dead zones and pockets may appear that are filled with dangerous levels of hydrogen sulfide. Therefore, it is important to regularly agitate, mix the soil in the aquarium and, again, siphon it. Some types of bottom filters have carbonate cartridges for chemical filtration.

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Aquariums that use bottom filters tend to be too high in nitrates and phosphates if they are not properly maintained. Weekly cleaning of the ground along with a water change is necessary to maintain the health of your aquarium system.

These filters are usually in the low and medium price range, depending on whether they have additional filter materials (cartridges) and running water under the plate. They can be used in various aquarium systems, but the number of aquarium inhabitants with a bottom filter is limited. In addition, bottom filters are not recommended for freshwater aquariums with aquarium plants (herbalists), as plant roots can grow into a gravel pack and impede water supply.

External mounted (power) filters

“Power Filter” – this term is used to describe the vast array of filters available on the market, which are suspended on the back of an aquarium. Most of these filters use all three types of filtering and are very easy to maintain. Such devices are equipped with a pump capable of drawing the required amount of water into the filter and are completely self-sufficient. Aquarium water is drawn into the filter using a U-tube and passes through a cartridge or other type of filter material. Most models have filter cartridges containing activated carbon. For each specific filter model is designed its own type of cartridge.

Mechanical filtration is carried out with the passage of water through the filtering material – synthetic winterizer and foam rubber – and is moderately effective. A weak point in the mechanical filtration of all electric filters is that the cartridges tend to clog quite quickly, making it difficult for water to pass through it. Therefore, it is very important to clean the filter regularly and wash the filter material. The frequency of cleaning and replacing the cartridges will depend on the biological load on the system.

For chemical filtration, as a rule, a filter cartridge containing activated carbon is incorporated. In some models, there are chambers in which more specialized chemicals and resins can be added. Chemical filtration efficiency is similar to mechanical filtration efficiency and will depend on the percentage of water passing through the cartridge. Again, the biological load on the systems will dictate how often the cartridge and filter material must be replaced.

Biological filtration takes place inside the filter cartridge. The mechanical and chemical sections of the filter are a haven for a large number of beneficial bacteria that help carry out the nitrogen cycle.

The effectiveness of biological filtration in the cartridge is limited due to the moderate amount of oxygen present in the water passing through the filter substance. The disadvantage of these cartridges is that after they are replaced, you lose all the bacteria along with the old cartridge. Before replacing an old cartridge, you can put a new one anywhere in the aquarium or next to the filter so that the beneficial bacteria can grow before removing the old one.

Some mounted power filters have a bio-wheel. The bio-wheel is a biological filter because it has folds on the surface that rotate when water passes through it. The bio-wheel provides excellent biological filtration due to the fact that the surface of the folds is in contact with the air when the wheel rotates. These wheels require minimal maintenance, they need only be periodically washed in water taken from an aquarium to remove any buildup.

How To Choose The Right Fish Tank Filter

Due to the fact that power mounted cartridges are in the low and medium price range, as well as due to ease of maintenance, such filters are ideal for beginners. However, they are not suitable for freshwater aquariums with live plants (herbalists) and saltwater aquariums. Ideally, the surface of the water in a freshwater aquarium should remain intact so that the concentration of carbon dioxide in the water is maintained. All mounted filters violate the surface of the water, which makes them less suitable for an aquarium with plants with a carbon dioxide (CO2) supply system. The disadvantage of using this filter in a marine aquarium is again the movement of water on the surface, as a result of which salt deposits form on the walls of the tank and on the instruments. These filters can also be used in a marine aquarium, but be prepared for additional maintenance and potential damage caused by salt inlay.

Canister internal filters

Canister internal filters are usually located in an aquarium under water and perform all three types of filtration. They are available both in an assembly that has its own pump and in a modular form that requires an additional pump. Usually, in such filters, a U-shaped form of water intake is realized, in which water flows from the bottom and is discharged outside in a sprayed form or stream. As soon as the filter is installed in the aquarium and connected, water begins to flow into the canister through the filtering material (foam rubber, sintepon, etc.), then it passes chemical filtration through the filtering substance. After chemical filtration is complete, the water enters the last chamber containing the biological environment, where the nitrogen cycle occurs and the water returns to the aquarium.

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Mechanical filtration in a canister filter is far superior to it in any other kind of filter. This is due to the fact that the container of the filter is under pressure and the water is pushed through the filter material by force, which allows it to hold more solid particles. These materials or cartridges are in some cases capable of holding the smallest solid particles.

Chemical filtration in a canister filter is also most effective compared to other types of filters available. Again, this is due to the fact that water is fed through the filter material under pressure. Another advantage of the canister filter is that any material can be used as a chemical filter. Activated carbon is usually used by default, but other substances may be added. Special tools are designed to remove the widest range of chemical compounds and excess nutrients from the system and can be used in emergency situations for urgent cleaning of the system.

Biological filtration is limited due to the low concentration of oxygen in the water passing through the filter. There are many types of fillers that are used for biological filtration in this kind of filter: these are glass, ceramic rings, and porous gravel. There are canister filters, which include a bio-wheel rotating in an aquarium.

Canister filters are in a moderate price range and require an average level of service. The strength of this type of filter is the ability to install it in any type of aquarium. If it does not have a bio-wheel, it can be placed in an aquarium with live plants (a filter with a bio-wheel breaks the surface of the water and will reduce the CO2 concentration in the aquarium, which is bad for plant growth). Canister filters, with the additional use of biological filters, are an excellent choice for salt water aquariums and for live reef aquariums. In combination with a biological filter, a canister filter can be used very effectively exclusively for mechanical and chemical filtration. In any case, the filtering material for mechanical cleaning should be regularly washed to avoid the growth of nitrates in the aquarium. The frequency of cleaning will depend on the degree of biological load on the system, but at least once every 4 weeks.

Wet-dry external filters

Wet-dry filters are usually placed under the aquarium, below the water level, using a device that controls the flow of water from the aquarium. The filter consists of two boxes: one is in the aquarium, the other outside. U-shaped siphon water from the aquarium enters the outer box. When entering the external device, water passes through a preliminary mechanical filtration (usually through a spongy material) before it goes further into the main filter. At hit in the main filter water mixes up with air and through dispersion gets to chambers. After that, it passes through biological media and enters through the lower part of the chamber to another part of the filter, often called a septic tank. In this compartment, several filter materials can be used to clean various chemical substances, including chlorine and calcium. In the same compartment, there is usually a pump responsible for returning the water back to the aquarium.

Due to the fact that water is fed into the filter material with a weak pressure, mechanical filtration in such devices is very weak and the water is purified only from large solid particles. Chemical filtration is also very weak, for the same reason – the water in the filter moves by gravity.

Biological filtration in a wet-dry filter far exceeds all the types of filters described before. Firstly, the large filtering surface provides space to accommodate a colony of bacteria. Secondly, not only is the water sufficiently in contact with air, but the oxygen concentration in the filter substance is quite high. There are many types of fillers for wet-dry filters like plexiglass, plastic cylinders and live rock. When choosing a filtering material, consider the surface area to increase the level of biological filtration.

Wet-dry filters are in a high price range and require little maintenance. Because of their high biological filtration capacity, these filters are often used for commercial purposes, they are ideal for excessive overpopulation of the aquarium, and are used for both freshwater and saltwater aquariums. However, these filters are not suitable for use in aquariums with live plants due to excessive saturation of water with oxygen, which helps to reduce the concentration of CO2. To compensate for insufficient mechanical and chemical filtration, this type of filter is often combined with canister filters. Maintenance of the wet-dry filter requires a weekly flushing of the filter material and the addition of fresh water to the aquarium. For the box of water in the aquarium you need to make sure that it was always immersed in water, otherwise the pump may fail.

The general table of data for all considered types of filters.