There are very significant differences between pond filters and
pond bio filters and a basic understanding of the difference is
important. After selecting correct pond pumps, the challenge of
making pond water clean, clear and healthy is the most important
aspect of selecting equipment for garden ponds or any water garden
environment for that matter. Much of this challenge is accomplished
by using the principles of biofiltration to build fish pond filters
to suit the conditions.
In a swimming pool water is normally pumped through a sand filter.
This filter does the job of removing solids and particles that remain
suspended in the water, and if there is an automatic pool cleaner
it also removes those solids that settle on the bottom. This is
classical filtration namely the removal of solids from liquids.
However the filter in a swimming pool does not purify or clean
the water. This job is done by the use of chlorine-based chemicals.
In this way the water remains perfectly safe to swim in because
the chlorine kills all the harmful bacteria and sanitises the water.
Consider what happens in garden ponds where no chlorine can be used
to understand what fish pond filters must do. UV filters for ponds
or UV pond filters are not bio filters - they are designed to kill
algae in garden ponds. UV filters for water gardens are however
essential ingredients to ensure crystal clear pond water.
Food is thrown into the water, some of which is eaten and the rest
remains behind. That which is eaten by the fish is partly digested
and partly expressed as a waste product, which sinks to the bottom
garden ponds. The fish needs to urinate and this passes into the
water also. Fish also express impurities (nitrogen based chemicals)
from their system out of their gills. Fish pond filters as you can
see are different and they require biomedia to work well.
Here is an ideal opportunity for pathogenic bacteria to develop
and toxic chemicals to build up. This is exactly what happens, all
day every day! The need for fish pond filters to purify the water
in garden ponds can be seen to be essential.
If there were no means of purifying the water the fish would quickly
poison themselves. Every kid has had a goldfish bowl and cried when
a week or two later the goldfish suddenly died. The poor fish poisoned
itself to death because there was no equivalent to fish pond filters
in the bowl.
In nature all sorts of factors combine to keep natural waterways
healthy - these do not have fish pond filters designed for them.
In a garden pond however things are different. There are too many
fish for the volume of water, the fish are overfed, there are few
natural surfaces and plants to help clarify and purify the water.