It sounds as though two subjects are being discussed in this thread.

1) Fish toxicity. As I understand it, low pH will dissolve copper
pipes. Because copper is variably toxic to fish (dependent upon
species), this can be very bad, and suggests that avoiding the use of
copper pipes for fish is prudent.

2) Pipe integrity. As Hal points out, copper pipes used today contain
alloys that do not stand up well to high temperatures and/or high flow
rates. They degrade (independently of pH), but do not leach copper at
excessive rates (unless pH is low) . In effect, the copper pipe
becomes a copper sponge tube. Might not be bad for fish, but leaks
are likely to occur.

Use PVC piping. Minimum Schedule 40.

Hal wrote:

On Tue, 17 Feb 2004 09:23:21 -0500, "Sam Hopkins"
wrote:

My guess is there's something more sinister going on. Copper pipes have been
used a long long long time in homes with water that is above 7 PH and the
plumping in them still exists after 80 years.

There was a flap about copper pipes not standing up to water here and
someone blamed impurities in the copper. Sounds reasonable to me,
but I'm not a metallurgist, just a tinkerer. At the time of the flap
most of the copper tube was being imported, can't remember which
country was making it cheap enough to ship it in cheaper than we could
make it here, but sometimes you get what you pay for.

Regards,

Hal