On 15/12/2017 11:11, Adam Funk wrote:
On 2017-12-13, Chris Green wrote:


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


I've kept freshwater tropical fish for nearly 50 years. Copper sulphate
is the traditional cure for snail infestations and some parasites.

Obviously too much will be toxic but at the right concentration it can
kill invertebrates but harmless to fish and plants.

I use a mixture of (cold) rainwater and (hot) tap water for weekly
changes, but the cylinder and pipes are probably so scaled up with
Hampshire's finest from chalk boreholes that it doesn't touch any copper.

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