On 2017-12-13, Chris Green wrote:

Adam Funk wrote:

That all makes sense, thanks. The other thing I thought of after
posting the question is that "outside" water might be acidic or
otherwise more capable of dissolving copper than drinking water is.

There's also the possibility that water animals (especially those with
gills?) may be more susceptible to copper than we are. Poisons can be
quite species specific sometimes.

Now that you mention it, I've seen aquarium instructions advising
against using hot tap water because it contains more dissolved copper
than cold.