> 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.