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Re: [APD] CO2 and pH control

Andrew wrote:
Also your way of thinking about CO2, pH and KH seems a little backwards to
me. pH is just something easily measured that comes about from a combination
of KH and CO2 that is easy to measure - it has no significance in itself, it
is purely an indicator. I can understand wanting to keep a low KH from some
fish (not plants), but then you just work out the target pH from the amount
of CO2 you want and the KH, and set for that. KH (and GH) matters to fish,
although usually not a lot, but pH does not.

Sorry Andrew, can't agree with you on this one.

>From the Algone corporate website:

"changes in pH are a common cause of fish fatalities. Fish can adapt to most
pH levels, if not broadly out of range, but they can't adapt to bouncing
levels........Keep in mind to change it [pH} slowly as it causes a lot of
stress to your fish."

"Some other facts about pH

Ammonia increases in toxicity with rising pH.
Nitrifying bacteria experience a growth and action reduction starting at a
pH value of 6 or lower."

pH certainly does matter to fish. Ever wonder why fish that are transhipped
for Asia to the US or Europe don't die of ammonia poisoning, which they
produce continuously? A big reason is that the pH of the water in the bags
stays low enough to keep the ammonia mostly in ionized form, NH4+, which is
signifcantly less toxic than non-ionized ammonia, NH3, which becomes much
more concentrated at higher pH levels and higher temperatures as well. NH4+
+ NH3 = Total Ammonia

The following table comes from an article by Garrett Glodek in the June 1991
issue of FAMA Magazine. This info is referenced from an APD post by Neil
Frank. NH3 is the toxic form of ammonia.

Table 1.    Un-ionized NH3 as a percent of total ammonia (by
            temperature and pH).
                         Percent NH3 of total ammonia
    Temp                          pH
                6.5      7.0     7.5      8.0     8.5

    68          .13      .40     1.24     8.82    11.2

    77          .18      .57     1.77     5.38    15.3

    82          .22      .70     2.17     6.56    18.2

    86          .26      .80     2.48     7.46    20.3

I have been accused of having backwards thinking before, so no problem
there. But to say that pH has no significance for fish is spreading
dangerous misinformation.


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