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In This Buyer's Guide:
- Why do you need an aquarium
filter?
- Biological Filtration
- Biological
Filter Media
- Mechanical filtration
- Mechanical
Filter Media
- Chemical Filtration
- Chemical Filter
Media
- What are the basic
types of
aquarium filters?
- Aquarium Sponge
Filter
- Aquarium Box
Filter / Corner
Filter
- Aquarium Power
Filter
- Canister
Aquarium Filter
- Undergravel
Aquarium
Filter
- Which Aquarium
Filter is Right
for You?
Why do you need an aquarium
filter?
An
aquarium filter helps to maintain a healthy environment for all of your
aquatic inhabitants. A good aquarium water filter will keep the water
clear for
viewing, while providing water that is free from particulates and
toxins that are dangerous to aquatic livestock. There are three basic
types of aquarium filters: biological, mechanical and chemical. The
type of fish tank water filter needed will depend on the size of the
aquarium or fish tank, the
quantity of the inhabitants and the amount of maintenance the system
will require. Frequent filter cleaning and water changes are also
necessary. Aquarium filters may utilize a combination of any
of
the following types of filtration.
Biological Filtration
In biological filtration,
different types of beneficial bacteria convert nitrites and ammonia,
the toxic byproducts of aquarium waste, into less toxic nitrates. This
process is known as the Nitrogen Cycle, and in order for it to occur,
there must be an oxygen-rich area for these bacteria to grow (See Fig.
1). When
cleaning the aquarium filter media, it must be rinsed in aquarium
water, rather
than tap water, so that the beneficial bacteria needed for biological
filtration is maintained.
Fig. 1: The Nitrogen Cycle
Biological Filter Media
 
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Mechanical filtration
Mechanical filtration removes waste
and other suspended particulates from the water. The aquarium filter
media,
which may be in the form of foam, filter floss, pads, micron pleated
paper or diatomaceous earth, is designed to catch and hold various
particles as the water flows through it.
Mechanical Filter Media
  
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Chemical Filtration
Chemical filtration removes dissolved waste from the aqarium. Chemical
filter media can
also remove toxins such as phosphates, ammonia, nitrates and other
toxins. Coupled with biological filtration, chemical filtration can be
a very effective method and can cut down on the frequency of filter
maintenance and water changes. The most common media for chemical
filtration is activated carbon.
Chemical Filter Media
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What are the basic types of
aquarium filters?
Aquarium Sponge Filter
Sponge
filters provide an effective method of biological filtration. An air
pump draws water through a sponge-like material allowing for the growth
of beneficial bacteria onto the sponge (See Fig. 2). It is this
bacteria that
provides the biological filtration. Mechanical filtration occurs as the
sponge also traps particulates in the water. Chemical filtration is
nonexistent in this method, and frequent water changes are necessary if
this is the only form of filtration used. These filters have limited
use and are only effective in small aquariums with a small number of
aquatic inhabitants.
Fig. 2: Aquarium Sponge
Filtration
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Aquarium Box Filter / Corner
Filter
The
corner/box filter is a box that sits inside the aquarium in one of the
corners. It comes in various sizes for small to medium tanks and is
capable of providing all three types of filtration. Layers of floss are
typically used as the media for mechanical
filtration, along with activated carbon for chemical filtration. The
bacteria growing on the filter media provide biological filtration. An
air
pump draws the water through holes in the bottom, through the filter
media, and releases it out through holes or slits in the top (See Fig.
3). The
efficiency of all types of filtration are limited due to the low levels
of water flow and oxygen content. Frequent filter changes are
necessary, but difficult since the entire canister must be removed,
disrupting the flow of the aquarium. It is better to replace only half
of the mechanical filter media at a time, in order to retain the
beneficial bacteria necessary for biological filtration.
Fig. 3: Aquarium Corner
Filter
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Aquarium Power Filter
Because
of their low price and easy maintenance, power filters are some of the
most popular on the market, and are great for beginner aquarium
hobbyists. As the name implies, the hang-on-back/hang-on-tank (HOB/HOT)
power filters
are designed to hang on the back of the tank and are capable of all
three types of filtration in one self-contained unit. The water is
drawn through a u-tube into the filter media, which in most cases is
contained inside of a cartridge (See Fig. 4). Power filters are
generally not
well-suited for freshwater planted or saltwater aquariums. Internal
power filters function in a similar manner, but instead of hanging on
the back of the tank, these may be completely submerged in water.
Fig. 4: HOB/HOT Power
Filter
Here are just a few examples of aquarium power filters:
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Canister Aquarium Filter
Canister
filters are external units placed beneath the aquarium (See Fig. 5).
These also
perform all three types of filtration, but are more expensive than
power filters because they are more efficient and very easy to
maintain. Because these filters are pressurized, they are highly
effective for mechanical and chemical filtration; however, biological
filtration is limited. Often, canister filters contain multiple trays,
with each tray providing a different type of filtration.
Fig. 5: Aquarium Canister
Filter Diagram
Here are some examples of aquarium canister filters:
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Undergravel Aquarium
Filter
An
undergravel filter is a slotted plate that is installed underneath the
gravel inside an aquarium, with multiple tubes extending upward toward
the water's surface. A power head is usually placed on top of the tubes
to draw water through the gravel and up through the tubes (See Fig. 6).
Biological
and mechanical filtration occur as the water passes through the gravel,
and activated carbon cartridges may also provide chemical filtration.
Although these filters are priced low, they must be maintained on a
weekly basis, due to the possible formation of dangerous hydrogen
sulfide gas within the gravel bed. In order to prevent this buildup,
the gravel must be vacuumed regularly and accompanied by frequent water
changes.
Fig. 6: Undergravel
Aquarium Filtration
Which Aquarium Filter is Right
for You?
There
are many factors to consider when buying an aquarium filter. When
making a selection, keep in mind that you must accomplish at least
mechanical and biological filtration. Certain filters are better at
biological filtration than others. You may want to consider
supplementing a power filter or box filter unit with a sponge. This
will provide a larger surface area on which beneficial bacteria can
grow, further supporting the existing biological filtration. Other
factors to consider are the size of your aquarium and flow rate.
Corner/box filters work best in smaller tanks, while power or
undergravel filters are typically used in mid-size tanks. The rate at
which water flows through the filter also impacts the success of any
system. All water in the tank should be run through the filter at least
four times each hour.
Whatever your choice, ease of
maintenance is also important to consider. Some filters require more
frequent water changes. Undergravel filters require weekly gravel
cleanings as well. Typically, higher-priced filters are more efficient
and easier to maintain.
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