Page 37 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

FILTRATION AND AERATION 35

Undergravel filters—which are now used less commonly, Powerhead mounted on airlift
compared with power filters—rely on a simple airlift system. A of undergravel filter
perforated corrugated or ridged plate is placed on the base of the
tank and then covered by a substrate of gravel. The plate allows
water to flow under the gravel, while the gravel particles— A powerhead, shown
above, is a pump that can
1
which should be at least ⁄8 in (3 mm) in diameter to ensure good be added to the airlift tube
water movement—form the biological filter medium. of an undergravel filter to
Power filters use an electric pump to drive water through draw water more strongly
the filtration media. There are two basic types: internal power through the system. Installing
a powerhead also improves
filters, which sit inside the tank, and external filters, which the aeration provided by
are housed outside the aquarium and are generally used for an undergravel filter.
larger aquariums. A range of different media are available for
power filters: biological media, possible to add additional materials—for example, peat or
such as foam sponge and ceramic coral sand—to this type of filter to alter the water chemistry.
granules; mechanical media, such Efficient aeration is vital for the maintenance of a healthy
as filter wool; and chemical tank, providing a source of oxygen not only for the fish but
filtration media, such as carbon. also for the beneficial bacteria within the biological filter.
The most efficient filters Using an air pump to pump air through an airstone (see p.41)
use layers of different media can help to aerate the tank: the bubbles produced cause surface
in combination. It is often ripples that increase the area exposed to the air where oxygen
exchange can take place. However, if there is enough surface
External power filters work on the movement generated by the outflow of the filtration system,
same principle as other systems, but an additional air pump may not be needed.
water is pumped out of the aquarium
and passes through the filter unit, which
contains one or several types of media, The small size of young fish, such as the
Cabinet hides External before being returned to the tank. Jaguar Cichlid (Parachromis managuensis)
unsightly equipment power filter fry seen here with their mother, means that
they are at risk of being sucked into a
power filter. Consequently, breeding
Airline tanks require less vigorous filtration;
AIR PUMP TIPS a simple sponge filter, pictured
left, is probably the
Filter Sponge traps best solution.
outflow particulate
waste
Airline with non-return valve Beneficial
• Fit a non-return valve in the bacteria
develop on
airline between the pump and surface
the tank to keep water from
entering the pump.
• If the pump gets noisier,
have it serviced or replaced.
• Never cover an external
pump; this creates a fire risk.

US_034-035_Filtration_Aeration.indd 35 29/08/18 4:08 PM