An impellor-driven water pump pulls water through a sponge filter in these filters. The sponge functions as a mechanical filter and also provides a home for certain nitrifying microorganisms. The sponge filter may be cleaned and reused several times, and with care, it will maintain the majority of its biological filtering capabilities. The sponge will eventually collapse and must be replaced; when this occurs, the majority of the biological filtering capacity is gone. By putting the fresh sponge in the aquarium for a length of time (preferably a few weeks) before it is required, it may be seeded with nitrifying bacteria. The lifespan of a sponge varies depending on the variety, but 6 to 18 months is typical. Sponge replacement costs are often low since more costly sponges survive longer than cheaper ones.
Internal power filters are available in a variety of sizes and water turnover rates. Higher turnover models often have bigger sponges, which give more filtering surface. Some models have a chamber for carbon or other chemical filtering material. Chemical filtering ability is restricted since they are often tiny.
These filters are best suited for smaller tanks. Their ability is limited by the area available for filtration rather than the rate of water turnover, as well as their restricted capability for biological filtration. They should also be used only in situations where biological filtration is not critical (for example, with reasonably resilient fish like as goldfish, coldwater species, and hardy tropicals) and are not ideal for marine tanks. (For additional details, see our marine fishkeeping lesson.) Internal power filters are an ideal addition to any tank with a high organic waste load since they assist clean the water and keep the main biological filter from getting clogged with debris.
To get the most out of this filtration system, choose the model that is suitable for the size of your tank and the number of fish. (Keep in mind that adequate filtration necessitates turning your tank volume over three times per hour; more filtration may be required if you have more or bigger fish.)
To remove biological materials from the sponge, gently rinse it in aquarium water (this will minimise loss of nitrifying bacteria). When changing the sponge, it is best to seed the new sponge with nitrifying bacteria before using it.
Clean the area surrounding the impellor every 2-3 months to guarantee smooth operation, and replace the impellor if required.