If it's milky white it's a bacteria bloom. These are millions if not
billions of free floating bacteria. As soon as they use up the nutrients
they should clear. There's "text book" concern that your fish will be under
stress because the bacteria utilize O2. I've personally never seen it kill a
fish though.

"Alan" wrote in message
om...
Hi

We have a pond which ha been self sustaining for twenty years. No
filters or pumps, just pond plants and regular cleaning out of debris.
The fish are healthy and we have only ever lost one occasionally to
what we have assumed to be old age!.

The water has recently turned a milky colour and this has not happened
before. The fish seem OK but is there anything I should be doing to
correct this?.

Alan