My builder also plumbed in a Nature 2, but my filter is new, sitting in the box.. (hmmmm wonder if I should sell it on ebay? Is there a shelf life? )

One person last year reported a bloom every time the Nature 2 would need to be replaced, so it had to be doing something. That's the only evidence I read that it works.

Personally, I think it's better to use less chemicals and avoid a bloom rather that keep putting metal in to keep it in check.

Robert