A filter is essential for maintaining clear water in an
aquarium. For fish that require extremely clear water, such as cichlids,
more than one type of filter should be considered. This also provides a
form of insurance in case one of the filters stops working. There are three types of filtration:
Mechanical - removes particles from the water
Biological - provides areas for helpful micro-organisms to
Chemical - changes water quality by adding oxygen or
The External Power Filter is very common and inexpensive.
It draws water from the tank and passes it through filter material such as
sponges, carbon and zeolite. The sponge can provide mechanical filtration
by removing particles. It can also provide biological filtration by
providing a perfect surface for micro-organisms to grow on. Rinse the sponge
instead of throwing it away - it is housing valuable life forms that can't be
Power filters often contain zeolite to remove ammonia and carbon to increase
oxygen content. This is referred to as chemical filtration. The
carbon and zeolite should be removed when using medications, to prevent the
medication from being quickly removed from the water. Evaporation is
significant with External Power Filters, but less than if a Bio Wheel is
installed.. External Power Filters are sold with aquariums from Walmart.
Brand names include
from Hagen, the Regent, which is produced by Marineland and the
Liberty, which is
produced by Eheim.
Comments by LittleHippyGirl: Aquaclear filters are great because...
-Have lots of space for beneficial bacteria
-You can easily customize the filter (ex: more bio-max, 2 sponges, add chemical
-You can easily add or remove a pouch of carbon
-You can adjust the flow rate
Can you tell these are my favorite HOB (Hang on Back) filters?
If you have a 30 gallon tank, an Aquaclear 300 should be all the filtration you
need, and depending on the size and strength of your fish, you probably want to
run it on a lower setting. Remember to never ever clean the bio-max, only the
sponges when they clog. If you do, you could upset your nitrogen cycle. Also,
added filtration doesn't really get rid of waste, it just moves it. Regular
water changes and siphoning is the best answer.
Comment by Tim: Aquaclear
filters do tend to stick after they've been turned off. I use a pencil to
reach down and give it a spin while the power is on to get them going again.
The External Power Filter with a
Bio Wheel is more difficult to
obtain, but is highly recommended for its biological filtration.
Micro-organisms develop in the wheel and the constant aeration from the turning wheel increases
the capability of these life forms to convert harmful ammonia, as well as supplying
oxygen to the water. The filter is replaced, but the bio-wheel is
With a Bio Wheel, gravel is not necessary as the
wheel provides all the necessary biological filtration. Bio Wheels have a
downside, in that they will put fish at risk if the wheel stops moving, as half
the helpful micro-organisms will no longer be available. A Bio Wheel also increases
evaporation even more than a simple External Power Filter. Make sure you
remove water instead of just topping up for evaporation, to prevent minerals
from building up in the aquarium. Bio Wheels like the
Penguin and the
are sold by Marineland.
The Eclipse Bio Wheel
by Marineland places the filer in the tank and in the canopy, so the
aquarium will fit flush against a wall on an aquarium stand. The Eclipse places
the fluorescent lighting at the front of the tank, so your fish are better lit
for viewing. Want to turn your Regent filter into a Penguin filter? -
The External Canister Filter allows the filter to be
placed competely out of sight. The most commonly available external
canister is the
Fluval Canister Filter
made by Hagen.
These come with tubing to position the canister out of sight. They also
allow a number of media to be added to the canister, such as zeolite, carbon and
peat. They are mainly useful for chemical and mechanical filtering.
The Wet/dry Filter
is also known as a trickle filter. It uses a pump to remove water from the tank and then pass it down a tower.
The tower is filled with material such as bioballs for biological filtration. The filter material is continuously
exposed to water and air, thus increasing the capacity for helpful bacteria to form in well oxygenated water. This
explains the term wet/dry.
The wet/dry filter is similar to a power filter but allows the water to flow completely down past the
filter while still exposing the filter element to air. It is also larger and more powerful than a power filter.
Wet/dry filters can also have chemical and mechanical filtration devices attached to them. Wet/dry filters require
very little maintenance, but, as with the power filter, evaporation is a problem. There are numerous varieties of
wet/dry filters and it is common for aquarists to build their own version.
Under Gravel Filters are readily available. They provide
one of the best methods of biological filtration. An air pump provides
circulation, which draws water through the gravel. This promotes excellent
micro-organism growth to convert harmful ammonia in the tank. One reason the
Under Gravel Filter isn't as popular as other filters is because areas of gravel
not covered by the filter can become toxic. If your Under Gravel
Filter doesn't cover nearly all of the bottom surface, it shouldn't be
used. Be careful about turning off the air pump too, since this will kill
micro-organisms and cause an ammonia spike. Despite these downsides, an Under
Gravel Filter can outperform an External Power Filter with a Bio Wheel.
The underground filter will also need an air pump to power it.
Rena makes an air pump which is highly rated.
The Internal Canister Filter uses air to force water through a filter
material in the tank, such as a sponge or days gone by - fiber glass.
Internal canister filters are not frequently used in home aquariums as they take
up valuable tank space and they are unsightly. They are sometimes used in
retail stores and wholesale operations. The
is an inexpensive example which actually omits the canister. The sponge provides both
mechanical and biological filtration. More expensive models include the
Rena canister filter by Aquarium Pharmaceuticals, the
and the Magnum canister filter by Marineland. Many retail stores use more
complicated systems which remove the water from the tank, filter it and return
it. These systems can include pumps that change the water at the same