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Re: CO2 Regulation

I am not a user of bottled CO2, so I am only a bystander to this long and
knotty thread, but I remember seeing or hearing about a pH measuring device
that had an indicator dye, probably bromthymol blue, in some kind of
plastic container that you submerged in the aquarium.  The plastic
apparently is permeable to hydrogen ions, but not to the indicator dye, so
that the pH can change as the tank pH changes without any of the dye
escaping.  This indicator device would be quite useful for some of the
problems mentioned, namely the drifting and aging of pH electrodes in
controlled systems and the increase of flow because the regulator is not
coping with a drop in tank pressure in systems that only use a regulator.
The value is that, with a glance, you can see if the pH has changed.  When
you have CO2 levels where you want them, the color of bromthymol blue is
green.  Every day you check your tanks and if the color is green, the
system is working.  If it is blue, the tank is not getting enough CO2.  If
it is changing towards yellow, then the rate of addition is increasing, and
it is time to check the system.  This type of indicator does not solve the
problems, but it allows you to catch these problems in their infancy before
you have the fish at the top gasping for air.

I havn't purchased this kind of pH measuring device, and so I am endorsing
it only on theoretical grounds.  If it works like I think it does, it
should be very useful in keeping a close watch on your pH.

Paul Krombholz, in bone dry central Mississippi