> The same problem could be encountered in either case, you are drastically
> increasing the partial pressure of CO2 in the reactor and the filter.
Drastically? I don't think it is that drastic. Certainly there is
an increase in both, but we are only dissolving a few bubbles per second.
The pressure in the canister is only the pressure applied by the columns
of water in the pipes.
> This causes the water to saturate and perhaps supersaturate for
> dissolvable CO2.
CO2 saturation at room temperature and pressure is probably
around 800 mg/l. In my tank, the [CO2] is around 25 mg/l.
The water then comes out of the reactor etc and suddenly
> the partial pressure drops and some CO2 may come out of solution as
> bubbles. This would be worse if either was under extreme pressure as the
> pressure drop alone can cause this effect.
You're right, this COULD happen, but I don't think that it does
under our aquarium conditions. Also, the pCO2 is dropping when the water
leaves the filter BUT the [CO2] is also dropping when it enters the tank.
> The problem would be nasty if the supersaturated water was inside the
> fish and someting caused the gas to come out then. I have a bit of
> trouble envisioning this situation in an aquarium, but I am sure that
> some of the inventive people on this list may think of something( eg
> suddenly deliberately applying a vacuum to the tank).
My bottom line is that the idea that "pressurized CO2 reactors"
can cause "the bends" is possible, but not plausible in our aquaria.