~ jan JJsPond.us wrote:

I'm sorry, but I just have to disagree with this one point. Since we have
no idea if the PWP (Person With Problem) even has decent water to exchange
with. Locally we have people take it straight from the irrigation canal
with no idea that the controllers add strong algae periodically.

Did you mean algicide? Anything's possible in this wacky world, but why
anyone would add algae is beyond me (a massive "algae-scrubber" filter,
perhaps?)

Plus, and I restate, if there is ammonia, can make things worst
with a water exchange
of higher pH. At a bare minimum people should have an ammonia tester.

I'm not sure. The math is too hard for this time of day, but intuitively it
seems to me that if your pH is low enough to protect the fish from ammonia
(and as Ingrid points out, it doesn't eliminate the toxicity only lower it)
if you did a 50% water change with even pH 9 water (assuming ammonia free -
this is _not_ necessarily a valid assumption, especially if you're using
chloramined water), you couldn't worsen the ammonia toxicity. However, if
you're using municipal source water, these days, you almost guarantee that
every water change adds ammonia.
--
derek