I did not know this. How come we are always told to use something like Novaqua to remove copper and other heavy metals from tap water?
Probably to sell Novaqua. Shrimp are known to be more sensitive than most freshwater fish. Saltwater fish are supposed to be more sensitive, too. I'll bow to other people expertise on specific species metal sensitivities.
I do want the tank shiny but I could have just the outside done if the copper and nickel oxidized surfaces are truly aquatic flora and fauna safe. Wouldn't water turn the copper pipes green?
A lot of things will turn polished copper, brass, and bronze colors. The patina seals the surface. Synthetic varnish will protect the shiny finish and shouldn't wear too much. Polished brass door hardware is sealed after polishing. It wears thin after years of use but you probably aren't going to be man handling the plumbing or corners of the tank often.
Since you can't see it, let any algae stay in the corners or use a soft sponge to clean those areas.