Back        Algarde Under gravel Filters Algarde one piece  undergravel filter.  complete with uplifts, airstones, airline. Undergravel filter to fit 12 x8"  aquarium actual undergravel filter size 11" x 7"              £3.99 Undergravel filter to fit 15 x8"  aquarium actual undergravel filter size 14" x 7"              £3.99 Undergravel filter to fit 18 x10"  aquarium actual undergravel filter size 17" x 8.5"              £5.99 Undergravel filter to fit 24 x10"  aquarium actual undergravel filter size 23" x 8.5"              £5.99 Undergravel filter to fit 12 x18"  aquarium actual undergravel filter size 11" x 17"              £6.99 Undergravel filter to fit 12 x30"  aquarium actual undergravel filter size 11" x 29"              £9.99 Undergravel filter to fit 12 x36"  aquarium actual undergravel filter size 11" x 35"              £9.99 Undergravel filter to fit 12 x48"  aquarium actual undergravel filter size 11" x 47"              £10.99 Undergravel filter Spare uplift tube assembly 1" diameter replacement uplift tube for Algarde undergravel filters (can be used with other systems), cut to fit height of aquarium.    £2.99 Filtration the natural way The under gravel filter is placed on the aquarium bottom an a layer of gravel is spread over it to a depth of 25mm-50mm(1"-2"). The design is such that the weight of the gravel and water seals the outer edges of the filter plate to the bottom of the aquarium, thus enabling only filtered water to enter the sub gravel area via the slots in the filter plate. When the air lift which is attached to the dome is operating, the air rising in the tube lifts water upwards with it from underneath the gravel and a circulation of water its thus created. The water in the aquarium is drawn downwards and filtered through the gravel into the filter plate and is then expelled by the air-lift towards the surface of the water. Any organic matter which is present in the water is drawn downwards onto the surface of the gravel where the micro-organisms, present at this level, break it down by a biological action and render it harmless. The filter bed matures over a period an probaly represents the best artifical approximation of the streams and waters of the fish's natural habitat. For Freshwater and Marine Aquariums Simple secure assembly Power by air pump or power head Optimum design for even water flow Can support heavy decor Directional flow return with fish guard