A sump filter is a type of filtration system commonly used in aquariums and ponds. It is typically located in a separate container or sump below the main tank. Water from the aquarium flows into the sump, where it passes through various filter media, such as sponges, activated carbon, or bio-balls, to remove impurities and maintain water quality. This filtration method is popular because it provides efficient mechanical, chemical, and biological filtration. Additionally, a sump filter can help with water circulation and temperature regulation, making it an essential component for maintaining a healthy environment for aquatic life, such as fish and plants.