I've been using tap water for a decade and never had bad results.

--
Don
"George" wrote in message
.. .

"david williams" wrote in message
...
HI,
My filter seems to soon fill with a browny green sludge. Should I clean
it
or will cleaning it destroy the bacteria i need?


Take a bucket and fill it with some of the pond water. Rinse it out with
some
of this water. Don't use tap water.