Here’s the secret to having the most efficient filter for a pond. Many people will have a bog filter, but will still end up with a green pond. There’s a couple reasons for that, which MOST people miss and what we have learned with getting our hands wet in hundreds of ponds.
1. Section a part of pond for a veggie filter.
2. Use PVC and tail to the edge of the pond
3. Drill holes in the PVC to draw water into from a pump.
4. Place lava rock over the PVC
5. Plants in lava rock
6. Pull water from PVC up and out of the pond to a UVC sterilizer.
7. Return water back to pond.
For much more information, take a look at the resources.
Clear Pond
http://www.americanaquariumproducts.com/ClearPond.html
Pond Clarification
http://www.americanaquariumproducts.com/AquariumUVSterilization.html
Pond Veggie Bog Filter
http://www.aquarium-pond-answers.com/2007/03/pond-veggie-filters.html