Re: [APD] CO2 and pH control

["Robert T. Ricketts, Jr." <rtricketts at verizon_net>]

Liz wrote, in part:
>
>I have some questions about how true that really is, mostly because pH
>swings of more than 1.0 happen every time I do a water change and the fish
>don't fall over dead from it.  Extreme changes of pH -- 3 units or
>so -- appear to whack fish.  I've seen some people import apistogrammas and
>have a box of 50 die within days of dumping them from pH 5 to pH 8 water.
>However, I have some questions about how much of that is strictly pH and
how
>much arises from the change in osmotic pressure.

With that I strongly agree. Fish do not "read" pH.  Fish are sensitive to,
and respond to,
the osmotic pressure of the water.  Changes in pH from less or more CO2 have
trivial effects
on the osmolarity of the water in relation to the same pH effect resulting
from added bicarb
of phosphate "buffers", so have correspondingly little effect on the fish.
Hobbyists get
frantic over pH differences without considering why the pH is different.  If
it is because the
tap water is loaded with dissolved gases, including CO2, that is not going
to harm the fish
from the pH as such (although the gases themselves may present different
issues as they come
out of solution).  Certain ions (Ca++/Mg++) may have negative effects on the
egg membranes of
blackwater fish, but their effect on the fish is trivial.  Those ions, not
the pH of the water,
are the real issues there.

Liz further wrote:

>I expect that eventually, as the myths go away, we will discover that the
>keeping fish was hampered by large amounts of information that was either
>wrong or very much overstated.  That's has been the case with orchids,
>another expensive, exotic hobby that was filled with misinformation for
>decades.

And with that I equally strongly agree.  How much "shared wisdom" do we
discard due to new
and better understanding of the real circumstances in our glass boxes?
Shall we discuss
the "knowledge" that phosphate causes algae?

Dave wrote, in part:

>I am citing
>published sources. Here is another article written by a Ph D. level
Kentucky
>State Aquaculture Specialist basically echoing what I previously cited:
>http://www.ca.uky.edu/wkrec/pH-Ammonia.htm

>Is this specialist and the other hundreds of articles online saying the
>exact same thing all spreading myth?

This is confusion.  The referenced cited gives 2.7mg/L ammonia-nitrogen as
the concentration
in a fish culture pond.  Anyone who has an ammonia-nitrogen concentration of
that magnitude
in their tank has problems to deal with, the pH being among the more
trivial.  Granted, the
difference between ammonia-nitrogen and total ammonia (as most of our tests
read) is not nearly
as different as those seen with NO2-nitrogen and NO3-nitrogen, but that
figure given is totally
off-scale for any other than a brand new hobbyist's tank.

This is part where and how myths arise.  I do believe someone said something
beautifully apt about
"a little knowledge is a dangerous thing...".  When you consider the
"normal" concentrations of
ammonia in our tanks, and the total pH swing possible/likely in our tanks,
being concerned about
the proportions between ammonia and ammonium ion is akin to being concerned
that a meteorite is
going to take out your skylight and the tank beneath. There are many far
more meaningful concerns.

RTR



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