The filter is the most necessary component of an aquarium. It is his heart. Choosing an appropriate filter is crucial for the water quality of the aquarium and therefore for the well-being of the living organisms.
A filter performs various tasks in the aquarium. Its primary function is biological purification, the decomposition of toxic nitrogen compounds created by fish feces so that water remains viable for fish. In addition, it cleans the water from various dirt, performing mechanical cleaning. Properly placed in the aquarium, it flattens the surface thus allowing gaw exchange and oxygenation of the water. It causes a stream of water in the aquarium, which is necessary for its proper functioning. From there on, depending on the type of filter, chemical cleaning can be achieved, that is, removal of various metals and toxins from the water using special materials.
There are several types of filters, the two main categories being internal and external.
The internal filters are located inside the aquarium. They are devided into simple internal filters, biological filters and bottom filters.
Simple internal filters are both the most economical and the least powerful. They are small enough not to disturb the aquarium but their active volume is small. They usually only have a sponge for mechanical and biological purification, and some contain a small amount of activated carbon for water purification. Their maintenance is very easy. It is a good aquarium with simple internal filters not loaded with a large volume of fish. They are suitable mainly for small aquariums, up to about 60 liters.
Biologicals are much more bulky and much more efficient. They allow the use of large volumes and a variety of materials. Their main disadvantage is the large volume they occupy in the aquarium. With the right choice of materials and pump you can support high aquarium fishing. They are suitable for all aquariums and easy to maintain.
Bottom filters use the bottom as filter material. Proper installation can be very efficient in biological filtration of the aquarium but they have high bottom maintenance requirements and should be accompanied by a second filter for mechanical and chemical water purification. Recommended for medium-sized fish tankers. Properly positioned they can be used in all aquariums. It is not recommended for aquariums with cichlids, as they tend to move the seabed.
The outer filters are located outside the aquarium and are separated into canisters and sump filters. All external filters can support high fish loading.
The canisters are very high performance and easy to use filters. They are easy to maintain as they are out of the aquarium. They have a large volume an a variety of materials can be used depending on the requirements of the aquarium. Their disadvantage is the higher cost of the interior and that they have to be lower than the aquarium before they can work. So it is good to have some furniture to hide them. They can be used in aquariums from 60 liters up to about 1500 liters. The combination of efficiency anf flexibility that they offer make them extremely popular.
Sump filters are specialized filters that require special installation to be installed and operated. It is a second bowl that is placed under the aquarium and communicates with it through pipes passing through the bottom of the aquarium. Sumps have the largest volume of all types of filters and are the most powerful filters. They are easy to maintain but must be handled carefully at the sump and aquarium water levels. Their placement is only in an appropriate aquarium furniture. Usually sumps are done with the aquarium, otherwise installing a sump later can be problematic to impossible. They are usually used in large and very large aquariums.
There are other, specialized types of filters, but they go beyond the meaning of the article.
Choosing the right filter should always be based on not only the size of the aquarium but also on what fish the aquarium will inhabit, in order to have optimal living conditions and the least possible problems, so that the aquarium remains a home ornament!