basic question facing all hobbyists is what filter should
I use for my aquarium. This is not an easy question
to answer because it depends on many variables.
When choosing a filter one needs to consider the size
of the tank, the type and size of the fishes in the
tank, and the time one has to maintain the filtration
system. Im sure considering the tank size and
fish is something you have read before but how does
ones time factor into the decision? Quite simply,
every filter needs maintenance, some more than others,
and if you wont take the time to do the maintenance
then the filtration system will become ineffective.
The importance of ones time will be clear with
a few examples.
There are many standard types of aquarium filters.
Some of the most common are the undergravel filter
(UGF), the outside hang-on-tank power filter and the
canister filter. Many people would consider these
filters to be equals and would recommend any of them
as a filter for your aquarium. However, the undergravel
filter is not a complete filtration system. Furthermore,
the undergravel filter requires regular maintenance
just like the canister and power filters. But in reality
how many people really maintain an UGF? In fact, how
many people know how to maintain an undergravel filter?
Now to the long-term hobbyist this may seem like a
crazy question but I have talked to many people with
undergravel filters who have no idea what a gravel
washer is for. As an aside: if youre reading
this column and work in a pet/fish store, I would
ask that when you sell a filter, any filter, take
a few minutes and go over with the buyer how to maintain
the filter. Conversely, when buying a filter ask the
sales clerk about how to maintain the filter. This
seems like commonsense but my experience tells me
that there are a lot of fish aquarium owners that
have little clue on how to maintain their aquarium
Consider the time and problems with maintaining an
undergravel filter. The goal is to remove dirt from
between the gravel on top of the filter plate so that
the water can flow freely through the gravel and contact
the nitrifying bacteria which colonize the gravel
grains. To do this, one has to siphon through the
gravel which can disrupt the decorations and planting.
You also have to completely remove the light fixture
and glass lid to clean the UGF effectively. Add in
that one needs to replace the airstones, the air pump
diaphragm, clean the inside of the lift tubes and
replace brittle airline tubing and this starts to
sound like work! This is why I feel that most aquarium
owners with undergravel filters, who know better, still
don't maintain them. Human nature is such that we
put-off those tasks that we dont like for as
long as possible.
Does your thinking that an undergravel filter is your
choice for that new aquarium change when you consider
the time and hassle factor of maintaining it?
Contrast the UGF with the modern power or canister
filter. The hang-on-tank power filters that are available
today are engineering marvels when you consider that
for less than $70 in most cases, they run 24 hours
a day, 365 days a year with little trouble and cost
only pennies a day in electricity to operate. One
can have a successful aquarium with a power filter
as the only filtration system. Service is convenient
and takes only a few minutes a month. Plus servicing
can be done without having to remove the light fixture
or the lid.
In general, hang-on-the-tank filters are for someone
looking for an easy to use, effective filter that
will need some routine maintenance such as changing
the pad. Fortunately, changing the pad is easy for
most hang-on filters and takes less than 5 minutes.
The old pad is lifted out of the filter and thrown
away, a new pad is taken out of the box or bag and
slid into the filter. In most cases, the filter does
not have to be turned off. How often the pad will
need to be changed depends on how much food is put
in the tank and the number of fish in the tank. Every
once in a while a more thorough cleaning of the filter
should be done. This means cleaning the inside of
the intake tube, cleaning the impeller and the area
where it sits, and cleaning the filter box.
Canister filters are generally more complex than a
power filter but they still have many convenient features
and can be serviced in 15 minutes or so. The features
that distinguish a canister filter from a hang-on
filter are they generally contain much more media.
Most canister filters can hold 12 to 15 oz of carbon
versus only one or two hang-on filters with that capability.
In the same aquarium situation, a canister filter
will generally run longer between cleanings than a
The drawbacks to canister filters include the continued
reduction in water flow as the filter clogs. As the
filter traps dirt, less water will make it through
the filter which means a lower flow back to the tank.
In extreme cases of filter neglect, the flow back
to the aquarium will be completely cut-off. This is
in contrast to the hang-on filter which will always
pump water back to the aquarium but that water may
not be filtered. Cleaning a canister filter is more
involved than a hang-on filter. To clean a canister
filter it must be taken apart which means dealing
with the hoses, valves, pump and other parts of the
unit. While not difficult, cleaning a canister filter
is more involved than cleaning a power filter.
Which filter you should use depends upon the type
of aquarium you plan to set-up and the way you approach
filter maintenance. No one filter will be the best
for every case, conversely none will maintain water
quality if they are not serviced. If you want a simple
filtration system for an aquarium that will not be
overstocked or overfed and you are willing to do
monthly filter maintenance, then the hang-on-the-tank
filter is probably the filter for you. Change the
filter pads at least monthly and every other month
clean the entire unit. The time needed for maintenance
is minimal but it must be kept in mind that the system
cannot be overwhelmed with fish or food.
If the tank you want to set-up is large and/or is
going to have a lot of messy fish then a canister
filter is the one for you. African cichlid tanks and
goldfish aquaria are examples of aquaria that would
commonly be filtered with canister filters. If you
are rather lazy about performing filter maintenance
(youll do it but probably every other month)
then a canister filter is a good choice. It will provide
a lot of filtration capacity and can be abused more
than a power filter.
Finally, to correctly answer the question of which
filter is best for your aquarium you have to be honest
with yourself. How much time are you willing to allocate
to servicing the filter? If the answer is as
little as possible then get a power filter with
easily changeable filter cartridges. If you think
the filter is too complicated dont buy it; youll
probably not service it often enough. Go with something
simpler that you understand. Dont be intimidated
by a sales clerk who is trying to sell you the latest
cutting edge filter and dont, for a second,
consider a filter which claims it does not need servicing!
Lastly, make sure you understand how the filter works
and what you need to do to clean it before leaving
So what filter is the correct one for your aquarium
- the filter that youll maintain on a regular
basis (and dont forget the partial water changes). □
© 2000 Dr. Timothy A. Hovanec