How does it work? This filter uses air bubbles from an external air pump or an integrated water pump to draw water through the filter. As water is drawn in through the lift tube or pump, it is replaced by water entering the filter. The top layer of white filter pad provides mechanical filtration. The black bio-sponge in the 2nd layer and ceramic rings with gravel provide biochemical filtration. They support the colonization of bacteria. The bacteria help break down harmful waste (ammonia and nitrite). What maintenance is required? The sponge needs to be rinsed out every time it gets dirty, about every 2 to 4 weeks. It helps to reserve the beneficial bacteria by gently washing the sponge with aquarium water instead of tap water. Measurements: 2.75 inches (L) x 3.15 inches (W) x 7.0 in. (H)
