Aquarium filters are available in all types and shapes to suit any need.
A good filter will provide for high water quality and keep the water crystal
clear for viewing. An aquarium is a closed system and must be maintained
by you, the hobbyist to optimum conditions. To achieve this ideal situation,
the right size and type filter must be used.
Before you buy a filter you should understand three different types of
water purification, I will explain them here before going on to the different
kinds of filters.
TYPES of FILTRATION
This is simply the removal of suspended particles of waste, excess
food, plant matter and general dirt from the aquarium.
Most filters employ some sort of mechanical filtration through filter
floss, pads or sponges that trap the waste as water passes through
This is achieved through the use of various media or resins placed
in the filter. This media removes dissolved waste materials such as
fish waste, etc., that can cause odors and discoloration of the aquarium
water. Chemical media placed inside the filter can also remove Phosphates,
Nitrates, Ammonia and many other toxins. The most common form of Chemical
filtration is the use of activated carbon.
The most misunderstood type of filtration, Biological filtration is
the process in which beneficial bacteria convert organics that have
been broken down into the toxic elements of Ammonia and Nitrite into
the less harmful compound Nitrate.
Nitrate can then be removed by water changes or chemical means. The
process of Biological filtration does not happen fast and usually
takes between four to six weeks to be established. The bacteria will
colonize all surfaces of the tank and filter. Some filters are designed
to promote these bacteria through the use of special media. Most complaints
of cloudy water are due to lack of a good bacterial filter, which
causes the bacteria to float freely around the tank.
TYPES OF FILTERS
There are many different types of filters available including:
I will explain each type here.
These are usually placed under the fish tank, hidden in the stand.
There are available capacity sizes from ten to hundreds of gallons.
They provide Mechanical and Chemical filtration and some have compartments
for Biological as well.
Hose intakes and returns connect the filter to the tank and can be
isolated through the use of valves. These filters can run a long time
between cleanings and maintain great water quality and are virtually
silent. My personal favorite are the filters made by the Eheim Company
- Power Filters
These are probably the most common of aquarium filters. They are easy
to install and maintain and provide both mechanical and chemical filtration.
Some newer types also provide for biological filtration.
These filters move large amounts of water and do a fine job of filtration.
They all hang on the back of the tank and are generally shaped like
this (square). All power filters
are a good choice for the new hobbyist.
- Under-gravel Filters
The sole purpose of this filter is to provide biological filtration.
It is a series of plates put under the gravel and water is drawn through
it, either by an air pump or power head. An additional filter must
be used to provide for mechanical filtration. This type of filter
has fallen out of favor, but still does its job and should be considered.
The latest rage in filtration, the wet/dry provides all three types
of filtration. It is large open filter that sits under the tank and
has sections for each of the types of filtration. You can even place
the heater in the sump of the filter.
Wet/Dry filters are mostly used by the mini reef community as their
higher water quality needs are met by this type filter. These units
usually do not include all needed items, pumps etc. Once set up the
maintenance of these filters is easy.
- Submersible Filters
These are small specialized filters that mount inside the tank. They
mainly provide mechanical filtration and circulation and can be used
in hospital or fry tanks. The units must be removed from the tank
for cleaning, making them not the most convenient filters to have.
They do have their uses and should be considered under certain circumstances.
- Diatom Filters
These are highly specialized filters used to "polish" the water. They
use Diatomaceous earth powder to coat a filter bag and filters water
down to microns in size. Due to the high efficiency of these filters,
they are to be used only sporadically and for short periods of time.
If you have more than one aquarium a Diatom filter is a good thing
Now that we have discussed the various types of filtration and filters,
what do we put in them? I have mentioned the term filter media before,
here I will explain in a little more detail.
There are a large amount of filter media available from almost every
aquarium product maker, for every type of filter. There are so many,
that the choice of which ones to use can be very difficult and sometimes
frustrating to find the one which will do what you want. I will describe
the three type of media here in generic terms.
- Mechanical Filtration Media.
This media is used to remove all sizes of free floating waste material
from the tank water. There are many kinds available, but they all
serve the function stated above. Some of the more common types are:
The mechanical filter media should always be placed first so that
any aquarium water must pass through it before the more expensive
media. Many filters come with custom made filter replacements that
fit perfectly and make replacement very easy.
- Biological Filtration Media
This media purpose is solely to provide a large surface area to promote
the growth of the beneficial Aerobic bacteria. This bacteria is responsible
for the nitrogen cycle and breaks down the deadly Ammonia and Nitrites
into the less harmful Nitrates. It to comes in many different forms,
all with a large surface area to size ratio. Some common shapes are:
Biological filtration is the most important form of filtration for
without it, the accumulation of fish waste will rise until the levels
reach a point where fish can no longer survive. The media is usually
placed in the filter after a good mechanical pre-filter to maintain
- Chemical Filtration Media
These media are designed to remove dissolved compounds that are not
wanted in the aquarium water. Each media is designed to remove a specific
compound and sometimes are combined together to make super cleaners.
Some of the compounds that can be removed through Chemical media are:
- Phosphates and Nitrates
The media usually come in their own bag and are placed in the filter
after the Mechanical media. They remove the compounds in one of two
ways, Absorption or Adsorption . Both ways provide high quality
filtration and can reduce the number of water changes, while at the
same time providing your fish with a cleaner healthier environment.