~ jan wrote, On 10/11/2007 22:22:
Recently mjl asked about filters. How about a thread with each ponder
either describing their set up or pointing to their website?

Here's mine.

Based in the South East of England. We have a 800ish gallon pond with 5
koi varying in size from 9-17", hand dug and lined with PVC.
Water is moved from the deepest part of the pond by an Oase in-pond pump
to the bio filter. This is the square tank from an old Oase
off-the-shelf filter system, but very modified. Water is fed in via hose
to the bottom of the tank where it enters a 2' diameter ring of 4"
perforated drainage pipe, this also incorporates aeration. Piled ontop
of this is the filter media, industrial floor cleaning pads cut into 1"
squares to a depth of about 12". Water rises through the filter media,
leaving all solids at the bottom, then cascades into a vertical exit pipe.
At this point it enters a small veggie filter (a 2x4' tank, with 6" of
water) filled with water cress.

Good points;
The main filter is only cleaned twice a year. Anything not broken down
by bacteria settles as a silt in the bottom. The bacteria is very
active, which I judge by it's high demands for oxygen when not aerated.
The veggie filter collects fine silt very quickly and provides a
plentiful supply of taste cress.

Bad points;
There is no fine filtering/polishing step. Little accidents that
introduce dissolved solids (plants being disturbed, too much messing
about) leave the water cloudy for a long time. The amount of fine debris
settling in the veggie filter indicates how much is in suspension.
Water cress has a fine root structure, but does not provide the dense
mat of filtration described by other people. We probably need a mix of
plants (?).

--
DavidM
www.djmorgan.org.uk