I think most of the smart folks here would advise you to test your water either with a drop-based test kit (like Ben's or the 5-way kit that may be available at Wal-Mart or a Taylor K-2005 or K-2006) or at a a pool store (don't buy anything there yet) and then post those results (Free chlorine, combined chlorine, pH, calcium hardness, total alkalinity, and CYA or cyanuric acid). People will be very willing to help you here once you've done that.
All that said, it's very likely that those same people will advise you to remove the cartrdige from your Nature2 unit so as to insure that you won't introduce any (more) copper or anything else into your pool water.
Cheers,
kv
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