Hi,
Here are some links to DIY filter systems.
Hope this helps.

http://www.mikebentley.com/ponds/homemadefilters.htm
http://www.animalnetwork.com/aquafish/reference/ap2.asp
http://www.wavepumps.com/state_of_the_art_filters.htm

Mark

"Ali" wrote in message
...
Hi,
A friend of mine recently moved into a farmhouse that has a small pond
(15 -
20 m diameter, 2 metre depth max,. a little through flow of water). I'm an
aquarium fish keeper, and he asked me about about filtering his water, to
remove algae which I presume is from nitrate/ite build up, and to give
greater water clarity. He has some koi / shubunkins (can't remember how
its
spelt). What I'm looking for is do you have a beginners faq or good web
links on how to build a decent, but not too expensive (he's just moved
house) filter. The usual one I have seen is with old hair rollers, and
some
foam matting.

Help would be appreciated.

Many thanks

A