| Filter Type |
Description |
Pros |
Cons |
Mechanical* |
Biological* |
Chemical* |
Typical Use |
| Under gravel (operated by an
air pump). |
The filter fits in the
bottom of the tank under the gravel. An air pump powered uplift circulates the water
through the gravel trapping particles and clearing the water. The gravel becomes the home
for bacteria which consume fish waste. |
Discreet. Inexpensive.
Reliable.
Can use carbon insert for chemical filtration.
Excellent biological filtration.
|
Difficult to clean. Not very good for growing plants.
Not ideal for digging fish.
Noise from air bubbles. |
Very good.
|
Very good. |
Very good but can only be
used with an air pump. |
Popular, traditional
filter. Should only ever be cleaned with a gravel cleaner. Under gravel
filters come in all sizes to fit any tank. |
| Under gravel (operated by
power head electric pump). |
As above, except a
power head circulates the water through the Under gravel. |
As above except almost
silent running. High turnover of water and increased water
circulation. |
Same weaknesses as above
except carbon cartridges cannot be used. |
Very good. |
Very good. |
Not available. |
Seen by many as an
improvement over air operated under gravels, especially if noise is an issue. |
| Internal Power Filter. |
A water pump circulates
water through a foam media which traps particles and becomes biologically active to treat
fish waste. There is also an option to pass the water through a chamber full of carbon to
remove other toxins. |
Very easy to look after and
to clean. Quiet running.
Excellent mechanical filtration. |
Care must be taken not to
over clean, should only be washed in mature aquarium water. Takes
up aquarium space therefore more obtrusive. |
Very good. |
Very good. |
Very good. |
Now the most popular type
of first filter. Available in sizes to suit aquariums up to
4ft. |
| Thermo-filter |
As
above but the filter also houses a heater which brings the water up to the
correct temperature |
As
above.
Only needs one plug
instead of two! |
As
above. |
Very
good. |
Very
good. |
Very
good. |
Popular
for smaller aquariums.
|
| External Power Filter
(Canister). |
Water is syphoned out of
the aquarium into a canister underneath the aquarium, full of filter media. It is
then pumped back into the aquarium. |
The most unobtrusive
filter. Very versatile.
Use any combination of filter media.
Infrequent, easy cleaning.
Silent running. |
Relatively expensive. |
Very good. |
Very good. |
Very good. |
Canister design has
improved so they are now very user friendly. Now appeal to
beginners, as well as experts.
For all types of aquarium over 2ft. |
| Sponge Filter (needs air
pump). |
Air powered uplift
circulates water through a sponge where it is mechanically and biologically filtered. |
Relatively cheap. Excellent for raising fry.
Ideal for smaller sized aquariums. |
No chemical filtration. Care must be taken when cleaning sponge.
More obtrusive. |
Very good. |
Very good. |
Not available. |
Only used in aquariums up
to 2ft. Ideal back-up filter for breeding, quarantine or
hospital aquarium. |
| Box Filter (needs air
pump). |
Air powered uplift
circulates water through a small box of media of your choice. |
Relatively cheap. Good back-up filter for carrying out specific tasks, i.e. carbon
filtration. |
Limited capacity. Obtrusive. |
Depends on which media you
pack into the box. |
Depends on which media you
pack into the box. |
Depends on which media you
pack into the box. |
Best used as a
supplementary filter. Or for smaller temporary aquariums for breeding etc. |
When it comes to
filtration there are a number of choices, which the beginner can find
confusing. The filter is perhaps the most important piece of equipment
for your aquarium and is essential for keeping the fish healthy and the
aquarium clean. The filter keeps the aquarium clean by removing waste
products from the water like uneaten food, decaying plant matter and
biological waste produced by the fish. The following table attempts to
explain the differences in filtration types.
*Mechanical
- this is the removal of suspended particles in the water, keeping the
water clear and the aquarium clean, so that you can see your fish!