There are a wide variety of filter options available for today's aquariums.
When choosing a filtration system, base the decision on the size of the
tank and number of fish. To achieve maximum results, you may need more than
one type of filter. Listed below are a few types that may suit your
Air-Driven Internal Filters - These inexpensive, box-like or foam filters
are ideal for small aquariums with very small fish. They are strong enough
to maintain good water conditions, but also gentle enough to keep fish free
of harm. Most of these provide mechanical, chemical and biological
filtration, and are placed conveniently inside your aquarium allowing you
to place the aquarium close to walls.
Undergravel Filters - As expected, these filters are placed underneath a
layer of gravel. They are air-driven and move water though the gravel,
creating favorable conditions for biological filtration; once bacteria
colonizes in the gravel they begin to break down waste materials. They are
small and often inexpensive. They can be run by an air pump or powerhead.
Models feature availability for both chemical and mechanical filtration.
Power Filters - These are among the most widely used aquarium filters. They
provide excellent biological, chemical and mechanical filtration. The
designs allow them to hang off of the back of the aquarium and are perfect
for tropical fish aquariums. Filter cartridges are replaceable, making
maintenance simple and convenient. Newer models feature either a biological
filter pad or bio-wheel to further filtration processes.
Internal Power Filters - These filters have the space-saving feature of air-
driven internal filter with the power and versatility of power filters. The
work great with circulating water since they are placed near the bottom of
the aquarium. These filters eliminate waste before it has a chance to
settle along the bottom. They are generally intended for smaller aquariums,
under 20 gallons.
Canister Filters - These provide superior biological, chemical and
mechanical filtration for larger aquariums or aquariums with a large number
of fish. Compared to power filters, canister filters require slightly more
effort to set up and maintain. These multipurpose filters are ideal for
saltwater aquariums, as well as freshwater planted aquariums.
Wet/Dry Filters - This type is the ultimate in biological filtration. They
are ideal for saltwater fish-only or large aquariums. They are called
wet/dry filters because the biological filter media is exposed to both
water and air. The design aid the production of beneficial bacteria. They
do, however, require the most effort to set up and are rather elaborate.
Most models are designed for placement under an aquarium and require an
overflow box on the back. Most wet/dry filters include a sump/reservoir
that holds auxiliary equipment along with the required water return pump.