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Fluval 303 Specifications

| Updated September 26, 2017

The Fluval 303 is a canister power filter, designed for use in both fresh water and marine aquariums. This canister filter has been manufactured to contain numerous filter media compartments. Aquarium water must pass through all the filter media before being returned to the tank, which ensures optimal chemical, biological and mechanical filtration is continually taking place. The Fluval 303 canister filter is typically positioned below the aquarium (Reference 1).


The Fluval 303 can easily be placed in an aquarium cabinet and has been designed to both operate and to be taken apart in the confines of the aquarium cabinet. The hermetically sealed motor of this power filter has been encased in epoxy and does not need to be serviced at all. The Fluval 303 incorporates valves that control the water flow and hose locks that ensure that both the hoses and valves remain securly attached to the body of the filter. These hose locks also prevent leakage and have been designed to be removed, when necessary, without the use of tools. The Fluval 303 incorporates a water return tube, which provides both oxygenates and agitates the water. By agitating the surface water, oxygen from the atmosphere is replaced and carbon dioxide is released into the environment (Reference 2).

Flow rate

The volume of water that passes through a canister filter each hour is important, as water carries oxygen to the beneficial bacteria that colonize the biological filter medium. The Fluval 303 has a flow rate of 130-gallons per hour and the water return system is made up of both rigid and flexible tubing, which allows this water to be directed anywhere in the aquarium. A rigid spray bar that allows for the all important, surface water agitation, has been included (Reference 3).

Filtration types

Mechanical filtration refers to the physically trapping of detritus and large pieces of decaying aquatic plant material and uneaten food. The Fluval 303 canister filter uses a foam inset to perform mechanical filtration. This canister filter incorporates activated charcoal as a chemical filter medium. The charcoal acts as a molecular sieve, in which potentially toxic compounds collect. All of the water entering the Fluval 303, is forced through the various filter materials before leaving the canister. The extended time that the aquarium water remains in the canister increases filtration quality which improves the functioning of the Fluval 303 filter. BioMax filter media is utilized by the Fluval 303 as a biological filter medium. BioMax provides an appropriate surface upon which the beneficial bacteria, which are responsible for the biological filtration, grow and multiply (Reference 4).