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What is the best filter? "Brenda
Shutter" <brendashutter@verizon.net> wrote:
> is there a best filter? sand filter like those used for a swimming
pool?
> pressurized filters? gravity flow? 55 gallon plastic drum? what is
best for
a
> 600 to 1000 gallon backyard cement fishpond?
samshutter_47@hotmail.com
Hi Brenda,
Unless you want to spend thousands of dollars on vortex filters or drum
screen
filters, the best filter for ponds in general are backflushable sand
filters.
For small ponds, however, it is much cheaper to install a simple
gravity feed
filter.
This consists of a plastic box with layers of open-cell sponge or other
suitable material. The layers of sponge etc. should vary from coarse to
fine.
The size of the filter depends not only on the size of the pond, but on
the fish
density, amount of suspended matter in the water, and the species of
fish (e.g.
koi stir up the bottom sediments). For an indication of size, you
should look at commercially available models. Basic gravity filters for
1,000 US gallon ponds (approx. 3,750 litres) are roughly one foot wide
by one and a half feet long by one foot high (300mm x 450mm x 300mm).
They typically have three or four sheets of filter material of varying
grades of fineness.
If you have more than a few fish or if the pond has a lot of organic
material in
it (leaves etc.) you will need to have some coarse filter material
placed in the
filter downstream from the sheets of sponge etc.. This can be
perforated plastic balls
(called bioballs) or rolls of plastic mesh.
If you are going to build your own filter, take a look at the
commercially
available models. For ponds with high fish density, double the size of
the
filter. For bottom stirrers like koi, double the size again. If the
pond is in a
warm climate and in the sun all day, double the size again.
If you have trouble with the water turning green and murky to see the
fish,
install an ultra-violet filter.
Pressure filters have the advantage of being easily hidden from view
but are not
as efficient as gravity feed filters in my experience. If you get a
pressure
filter, make sure it is back-flushable for ease of maintenance.
The best filter for a pond depends on three things:
1. The amount and fineness of suspended particles in the pond. The
greater the
amount, the larger the filter needed. The finer the particles, the
finer the
filter medium needed. This type of filter is called a mechanical
filter.
2. If your pond has many fish or if your pond has only a few fish but a
lot of
leaves and other organic matter getting into it, you will need a filter
which
has material which gives extra surface area for the attachment of
nitrifying
bacteria without restricting water flow. This type of filter is called
a
biological filter. Usually the biological filter media is placed after
the
mechanical filter media so that it doesn't become clogged with
suspended
particles. The amount of biological filter material needed depends on
the
density and species of fish in the pond, the amount of organic matter
(leaves
etc.) in the pond and the type of media used.
3. Whether the pond has "greenwater" problems. Ponds in warm climates
that get a
lot of sunlight usually end up looking like pea soup unless they have
an
ultraviolet (UV) filter (actually an ultraviolet light which kills
microalgae).
Microalgae is so fine it passes through mechanical filters. To remove
it, the
mechanical filter would need to be so fine that it would clog up in no
time
unless it was enormous in size. UV light not only kills the microalgae,
it fuses
the algae cells together to make particles large enough for the
mechanical
filter to remove. Needless to say, the mechanical filter media should
be placed
after the UV light.
Regards,
Lloyd Mathews. |
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