replace the biofilter media. it just gets silted up and wont rinse out very well
after a couple years. do you have fish in the pond?

On Tue, 15 Jul 2008 21:02:56 +0100, steiny wrote:
I have a small garden pond with a bio filter and external uv supplied
by a more than adequate pump. The pond has been up and running for a
good two years now and I have generally had no problems but recently
the bio filter has started to frequently block up and stop water flow.
I have unblocked it twice in the last two weeks which is unusual ...
can anybody shed some light on this or post any suggestions as to what
could be causing this. Cheers.