Rob,
Rather than depending completely on the stream for filtering
purposes, look to the reservoir, if you have one, at the top of it. I
would sink whatever filter you construct in there, and hide it with
floaters and marginals, and then the prefiltered water would undergo a
final "scrubbing" in your stream. Many people have veggie filters at
the top of streams as their filtering scheme. I don't blame you at all
for not wanting a big ugly filter in your pond. If you don't have a
pool at the top of your stream, maybe an above ground vessel would be
practical. There are lots of ways to approach it. I like the design
of the filter you were looking at, but it is a pain to clean, and I
have never had the effortless experience with them that others report.
It also looks small for a pond the size you describe. I had two
cannisters bigger than that, and we had to wash them once a week in the
summer. Of course, we had a good number of fish, but many people do
want a filter that will handle a sizeable fish population. Hope this
helps,
Ann