Another
kind of biological aquarium filter that is commonly used in aquariums is the
sponge filter. Although varying somewhat in appearance, all sponge filters work
the same way. Water is pulled through the sponge, which is colonized by
nitrifying bacteria. Most sponge filters use a single lift tube and air bubbles
to draw water through the sponge, although some large models can use a
powerhead instead.
There
are specific reasons for using sponge filters. For example, if you keep a
sponge filter in a tank that already has a biological filter; it will develop
its own colony of bacteria. The sponge filter can then serve as an emergency
biological filter in another tank.
If
you need to set up a small tank to treat a sick fish or a quarantine tank for
new fish, the sponge filter can provide immediate biological filtration for
that tank. This eliminates the usual break-in period.
For
those who breed fish, the sponge filter is also very useful. Often at some
point, young fish need to be taken out of the adult tank and put into a fry
tank, which contains only juveniles of the same size. Sponge filters provide
instant biological filtration for the fry tank.
It
is safe for the baby fish because there is no dangerous filter intake, as with
power filters, and the micro-organisms on the surface of the sponge even
provide an additional food source for the growing fish.
