Under-gravel Filtration

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Most modern aquariums use powered internal or external filters, before these were available, under-gravel filtration was widely used, and is still used by many aquarists. An under-gravel filter consists of a perforated plate placed underneath the aquarium gravel with one or more 'uplift tubes' By pulling water up the uplift tube, usually with an air pump or powerhead water pump, water is drawn down through the gravel, which acts as a surface for bacteria to grow on, and traps waste particles.

Whilst under-gravel filters work reasonably well, they are difficult to modify or to add specific media, and many modern powered filters are far superior.

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