Large aquariums need powerful and effective filters for the fish to survive. An aquarium with an ineffective filter will have dangerous chemical levels causing poor water quality. An effective filter on a large aquarium will rear the healthiest fish.
The two best filter types for large aquariums are canister filters and wet/dry filters. Both filters are installed outside of the aquarium and work best for large, fresh or saltwater aquariums.
These filters provide effective mechanical filtration, biological filtration and chemical filtration. These three filter steps are necessary to maintain healthy and stable water chemistry in large aquariums. Mechanical filtration removes debris, biological filtration removes waste and chemical filtration removes toxins.
A canister filter uses a pressurized pump to move water from the aquarium into the external canister container, forcing the water through biological, mechanical and chemical filtration. A wet/dry filter uses a siphon to move water into an external tank or container, trickling the water over mechanical and biological filter medium. Wet/dry filters can also incorporate chemical filtration.
Canister filters are recommended for tanks larger than 50 gallons, and wet/dry filters work for tanks as large as 400 gallons.
Canister filters have highly effective chemical filtration, but limited biological filtration. They work great on freshwater aquariums. Sump filters have highly effective biological filtration, but limited chemical filtration, which is beneficial for reef aquariums.