Page 36 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

34 FRESHWATER FISH: SETTING UP THE TANK

Filtration and aeration FILTRATION TIPS

• Add zeolite sachets to remove ammonia
An effective aquarium filtration system not only removes waste from the water and a starter seed culture of
bacteria for the biological filter.
products from the water by physical or chemical means but also • Be careful not to overfeed the fish and
mirrors the process of biological filtration—the nitrogen burden the filter with decomposing food.
cycle—that occurs in the wild. Filtration goes hand in hand with • Test the water quality regularly to check
the filter’s efficiency; frequent partial
aeration, in which water is circulated so that it can absorb oxygen water changes (see pp.50-52) will ease
the pressure on the filtration system.
from the air and lose unwanted carbon dioxide.

In the confines of an aquarium, the
waste produced by the fish can quickly NITROGEN CYCLE Ammonia is excreted by fish as waste and is also
build up to harmful levels without an produced when any organic matter decays
effective filtration system. Filtration Fish in the aquarium AMMONIA Beneficial bacteria
involves passing the water in the aquarium eat plant protein, (NH3) present in the biological
filter convert ammonia
completing the cycle
through one or several filtration media, which to nitrites
purify the water by biological, chemical, or The nitrogen cycle is a NITRITES
natural process by which
(NO2-)
mechanical means (see box, below). There are nitrogenous waste Nitrites are converted
two basic methods of driving water through the products are recycled. to nitrates by other
media: using an electric pump, or relying on an In biological filters in NITRATES beneficial bacteria in
(NO3-)
the biological filter
airlift system, in which air bubbled into the aquariums, growth of
the bacteria that drive
tank through an airstone draws water up an this cycle is encouraged. Plants absorb nitrates from the
water to use as fertilizer
airlift tube.
FILTRATION METHODS Clean water exits from the top of the pump
There are three basic methods of filtration: and may utilize all three. Many Power line
mechanical, biological, and chemical tanks have an undergravel filter,
(below). Aquarium filtration systems often shown below, which is a simple Suckers attach
involve more than one of these methods biological filter. Internal power filter unit to glass
filters (right), also provide
biological filtration but can Water passes up
Mechanical filtration uses a the unit, either
filter medium, such as this filter include additional media for through a sponge
wool, to sieve particulate waste purifying water by mechanical or through layers
from the water. The fibrous and chemical means. of different media
structure traps the waste,
which can then be removed. Water emerging from airlift creates Water is sucked into
surface ripples, improving oxygenation the unit at the base
Airline
Biological filtration involves Internal power filter An integral electric
the breakdown of waste by pump draws water through the filter unit,
beneficial bacteria that drive the which contains one or several chambers
nitrogen cycle. These multiply housing filtration media inserts. After
in media, such as this foam Water is forced Air flows down passing through the media, the clean water
the airline
sponge, and in the substrate. through gravel is returned to the main tank.
Airlift tube
Chemical filtration relies Bubbles emerging Undergravel filter Air pumped through
mainly on activated carbon from an airstone an airstone within an airlift tube draws
to eliminate dissolved waste draw water up water from below the gravel substrate.
from the water. Unfortunately, the airlift tube This forces the water through the gravel,
this process also neutralizes Filter plate which contains beneficial bacteria that
some medical treatments. with holes Water is drawn from break down harmful waste products.
below gravel

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