Wet/Dry and Sump Aquarium Filters are designed for use on larger aquariums, and are geared towards the more advanced aquarium keeper. These types of filters are typically gravity fed systems, which sit below the aquarium, inside the aquarium stand (there are also some hang on type models that are less common) These filters require the use of a Reef Ready type of aquarium (drilled or built in overflow), or the use of a hang on type overflow box to feed water from the aquarium to the filter. Water is then returned from the filter to the aquarium with either a submersible or external water pump. The return pump can be fitted with either rigid or flexible tubing. Many types and variations are available on the market. Basic models are fairly simple, while others can have multiple compartments, or be modular to function as needed. Wet/Dry and Sump filters are available for just about any size aquarium; standard models are available for aquariums up to 400 gallons.

Wet/Dry filters get their name from how they are designed to maximize biological filtration by keeping their filter media above or out of the water (dry) to increase available oxygen to the bacteria that colonize the filter. Filter design and media type can vary greatly, but all Wet/Dry filters work on the same principle. The bacteria that consume waste in the aquarium needs oxygen to survive and reproduce; submerged biological filters can be limited by the amount of available oxygen in the water. Filter media in a Wet/Dry filter is exposed to the air and aquarium water is passed over or through the media allowing more available oxygen for the bacteria to grow and consume more waste. Most Wet/Dry filters also incorporate a mechanical filter media to remove debris from the water providing a high performance, extremely efficient filter.

Sump filters usually do not incorporate a biological filter component, and will only have a mechanical filter, usually in the form of a filter sock. Sump type filters usually have a lot of open space, and are typically used on salt water aquariums, especially reef aquariums, for housing equipment like protein skimmers and media reactors. Sumps may also be used as, or include, refugiums for growing macroalgae or coral fragments.

Interested in other types of aquarium filters? Check them out here.