which filter for suspended clay?

Dear all,
We have a new large-ish wildlife pond, 10m (30 feet or so) roughly circular,
and about 5 feet deep in the middle. We have a problem with the local soil
being heavy red clay- as a result the water is permanently a greyish-brown
colour and water can't penetrate to plants. I've tried floculating chemicals
like "pond clear" but it has little or no effect- I think we would need
gallons and gallons of it for this size of pond. Can anyone suggest a filter
pump that can help us, without affecting the wildlife? If not, then what
filter/pump would clear the water the quickest, that we can run for a short
time before planting up?
Paul D.