An aquarium sump is a separate tank or container used in aquarium systems to enhance filtration and water quality. It is typically placed below the main aquarium and serves as a space for additional filtration equipment, such as protein skimmers, pumps, and bio-media. This setup helps to keep the main tank cleaner and provides a larger volume of water, which can stabilize water parameters. In addition to filtration, an aquarium sump can also house equipment like heaters and refugiums, which can promote beneficial algae growth. By using a sump, aquarists can maintain a healthier environment for their aquatic life while keeping the main display tank visually appealing and uncluttered.