How Do Fish Tank Filters Work?

Mechanical

When most people think of fish tank filters, they think of mechanical filters such as sponge, mesh or floss pads. Mechanical filters capture and help remove visible debris like solid fish waste, leftover food and pieces of plants or algae. Water is pulled through the filter by the aquarium pump. As water passes through the filter, debris is caught in the filter and removed from the water.

Chemical

Chemical filters remove toxins and impurities from the aquarium that could be harmful to fish such as liquid waste, ammonia or nitrate. The most common chemical filter is activated carbon. Other types of chemical filters are usually designed to deal with specific problems such as heavy metal found in some water. Chemical filters work similar to mechanical filters in that the water is pulled through the filter by the pump. The difference is that they capture toxins not through physical means, but through molecular bonding of the toxins to the filter material.

Biological

Biological filters are used to control bacteria levels in an aquarium. Controlling bacteria also reduces the amount of ammonia and nitrogen in the water, keeping fish healthier. It's important to understand, however, that biological filters don't remove all bacteria, but instead encourage the growth of "good" bacteria. The helpful bacteria breaks down waste so that it can either be used by aquarium plants in their growth cycle or removed by the other filter systems. The most common biological filter is a natural sponge on which bacteria is encouraged to grow. In home aquariums, it is usually placed behind or underneath the mechanical and chemical filters. Bacteria break down any remaining waste as it passes through the sponge.

Resources

• Doctors Foster and Smith - Aquarium Filter Maintenance