First, you should drain about a third of the water out, and remove any debris from the bottom of the pond such as sludge, leaf matter, etc. The easiest way to do this is with a shop vac. Be careful though, as it can pull in fish, frogs, etc.
Next, as far as equipment, I would recommend the following:
http://www.tetra-fish.com/Pond/Products/garden-fish-pond-equipment/ultraviolet-uv-clarifiers/greenfree-uv-clarifiers.aspx (UVC-5W would be the correct size)
http://www.tetra-fish.com/Pond/Products/garden-fish-pond-equipment/garden-pond-pumps/water-garden-pumps.aspx (550 GPH would be the correct model)
You would also need to buy tubing in the 1" and 1.25" sizes, as well as hose clamps. If you are on a budget, however, you could get by with: http://www.tetra-fish.com/Pond/Products/garden-fish-pond-equipment/pond-filters-filtration/pond-filter-kits.aspx. It does not come with the UV but has everything else you need. I would recommend hose clamps, and pea gravel as well. The pea gravel goes in the bottom of it and offers more filtration for you. This filter sits in the pond though, and can be a pain to pull out to clean since you have to pull both it and the pump up at the same time.
Date published: 2017-03-20