A canister filter is a type of aquarium filter that is typically placed outside the tank. It uses a sealed container, or canister, to hold various filter media, such as activated carbon and sponge, which help remove debris, toxins, and impurities from the water. This design allows for efficient filtration and is suitable for both freshwater and saltwater aquariums. Canister filters are popular among aquarium enthusiasts because they offer high flow rates and customizable filtration options. They can accommodate larger tanks and provide mechanical, chemical, and biological filtration, ensuring a healthy environment for aquatic life, including fish, plants, and invertebrates.