" wrote in
ups.com:

i previously had two canister type filters on my 2000g pond.one was
rated for 500g and the other for 250g. i thought one was rated for 750g
but 750g was it's max flow rate. these filters clogged weekly and i
could clean them in the morning and by sunset they would be very dirty
again. i don't want to clean my filters any more than a couple times a
month.

....

i have put together a 40g rubbermade tub filter. i have plumbed a 3/4"
intake and 2x 3/4" exhaust pipes which go into my waterfall. my
question, based on the above, is what kind of filter media should i
use? i currently only have bio-balls in there for biological
filtration. something for mechanical filtration would be good. i need
something cheap and doesn't clog easily. i don't care if it was
designed for ponds or not so long as it helps out and doesn't negativly
affect the life in the pond...


This season I’m trying something new for filtration, and so far it is
working well. It‘s inexpensive, the water is clear, and the fish are
healthy. I’ll describe my overall set-up, so that you can understand how
the filter works.

My system consists of 4 ponds. The top one is about 10 gallons capacity;
the water cascades from there into the second pond (about 50 gallons
capacity); from there the water cascades into the third pond (about 100
gallon capacity); and finally into the main pond (about 500 gallons).
The water is pumped from a submerged pump to the top pond. All the ponds
have water plants, mostly irises; the bottom pond has two large koi and
about 10 goldfish.

The filter system consists of a couple of flower pots - the black plastic
baskets with slits - intended for water plants. The baskets are filled
with gravel, approximately ¼" to ¾" irregular stones. The water leaving
the top pond and the water leaving the second pond discharges onto the
gravel, which extends a few inches above the water level. To exit the
baskets, the water must pass through the gravel.

I seem to have developed a low-tech, low-cost, highly effective
mechanical/biofilter. In a few months I’ll have a better picture on how
well it works.