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I never experienced pH shock in the 5 years I was breeding Angelfish and
Discus. I would have pH as low as 3.5 in some tanks and when it got that low
I would adjust the pH back to about 7.0 in a matter of minutes. No effect
(and we're talking several _thousands_ of dollars of breeding stock). The
only bad effects occurred when:
a) when I had measurable nitrite in a not-yet cycling tank, and
b) when the water came out of the tap with very low pH (due to CO2 in the
The way it was explained to me was it wasn't the swing that killed the fish,
but any NO2 at a low pH is very toxic as nitric acid (as I think Paul is
trying to say below with the chemical-ese). The effect is very similar to
having any measurable ammonia and what percent of it is toxic above 7.0. The
lower the pH (below 7.0), the more toxic NO2 becomes, the higher the pH
(over 7.0) the more toxic Ammonia becomes.
Therefore, as long as you have no NO2 and ammonia in the system you can
swing the pH with little, if any effect on the fish (except for maybe an
induction of spawning).
Kind of makes you laugh when the new guy at the LFS says "float the bag".
Imagine two tributaries coming into a river. Both temperature and pH on the
incoming trib is different than the main stream. Do you think the fish puts
one fin into the trib and wait 20 minutes before deciding to swim up the
trib? That he swims up and die within a day?
> No-one else jumped in on this - I think that NO2- is pretty toxic but that
> HNO2 is a good deal worse, and the pKa of HNO2 is about 5.2, meaning
> that the two will have equal concentrations at pH 5.2. At 6.2 there will
> be 10 times as much NO2- as HNO2, at 4.2 10 times as much HNO2 as NO2-
> - --
> Paul Sears Ottawa, Canada