Time to drain and refill?

[Salar]

Hello again. Thanks for the help on the grren water earlier, the pond is no longer green but it is still very murky. I would have liked to keep it "natural" but should I drain the pond, clean out the muck and refill with clean water to keep it clearer? It is a 400 gallon pond, so not huge, contains a few carp, plenty of weed, but is under trees. It was built 3 years ago and not drained since. It has a biological and UV filter, it is rectangular shaped, lined, surrounded by paving, with a spout-type fountain at the deep end (18"). Advice from more experienced folk much appreciated.

[chesters1]

try not to use tapwater to refill , if possible collect several dustbin fulls of rainwater or if you have to use tapwater let the pond "stand" for a few days before adding fish ,and never clean a bio filter under the tap as it kills the bacteria , there used to be an addative that removed chlorine and "aged" the water it may be ok in a total refill but i would keep a dustbin full of the old water to ensure that it wasnt completly sterile water the fish were put back in in the autumn stretch a bit of garden green netting (fine holes) across the pond to keep the leaves out and remove when theve dropped its probably the rotting leaves that makes the silt and the nutrients released the reason for the green prob