Aquarium filtration unit is one of the essential components of successful ornamental fish farming in a commercial scale. It is such a single unit which takes care to provide healthy environment to the aquatic animal by maintaining the water quality at the optimal level. The component, placement and size of the unit may vary with the type of farming system. Before installing a biofilter unit it is essential to have a thorough knowledge, or rather consult an aquaculture engineer as because this requires special know-how on working of a biofilter, mechanism and the biology behind the filtration process. The efficiency of the biofilter depends completely on living microbial population harboured in a 'stabilized' biofilter, a constant care and maintenance. The mechanical filters operated by airlift system fitted in aquarium needs maintenance for cleaning of sponge or poly wool. Gravel filter push the water through the gravel bed to provide a very large surface area on which the nitrobacteriums can live. The gravel bed should be 5cm deep for effective aeration of plant roots.