How do i clean a pond?

i have just moved into new home there is a pond in the garden it is 20ft long 8ft wide and about 4ft deep i know nothing about keeping fish in a pond it is a very cloudy green in colour and the fish seem to be gulping along the suface i've been told there is not enough oxygen in the water. There is a filter tank in the garage this is crystal clear but the water in the pond is not can anyone help?
Answers:
It sounds like the pond needs a water feature like a fountain to move the water around so there's more dissolved oxygen.

The green color you're seeing is from free-floating bacteria. This is fairly normal in the spring, as the days are getting longer and the weather is warming. The algae needs nurtients and light to grow, so the longer days are part of the problem - and inside the garage, there's not as much light, so the tank there won't support the algae growth. Once the water's warm enough for plant growth, floating plants (water hyacinth, water lettuce) and plants with floating leaves will help shade the water. They will also help by competing with the algae for nutrients in the water. For small ponds, you can even do water changes to help remove nutrients.

A UV sterilizer will help with algae control, but these don't come cheap - you also have to replace the bulb every 12 months or so, depending on how much it's used. Another option is to try bales of barley straw: http://montgomery.extension.psu.edu/nres...

Here are a few more links with some pond maintenance tips: http://www.wetwebmedia.com/pondsubwebind...
http://www.wetwebmedia.com/pondsubwebind...

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Empty the pond, take the fish out and leave in containers with enough water. clean the pond and check the filter works, refill, add the fish with the water they were in. Voila!

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if it is man made you will need to drown it and then clean it but if it's not then u don't clean it

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Check to make sure the pumps are working correctly. if the fish are gulping you need to get oxygen into the water you can do this by either agitating the waters surface with a water fall or fountain or add a large air stone hooked to an air pump. once the fish are ok. drain about 20% of the water and re fill do this once a week for the next month. go to the local pond shop or pets store with a clean 20oz bottle of you pond water and they will be able to test it for you and tell you what's wrong and how to fix it.

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if the pond water is green don't panic its normal,you can get it clear by way of a u.v which kills of any algae that passes through it? don't empty all the pond water as this will upset the balance of the pond? take out about a 3rd and top back up? do this over a period of a few weeks? as for cleaning any filth in the pond etc you can hire out a proper vacuum cleaner from any decent aquatic centre?