Gromberg says:
> Tyson, if you doubt what I say, try tank+FROG+gauge+needle-valve in that order
> and close the needle valve.  The gauge will rise to 800PSI or so.  CFM is not
> pressure, it is flow.  The FROG is a Flow Regulator, not a pressure regulator. 
> Flow and pressure are highly correlated, stop the flow and the pressure will go
> through the roof.  Don't injure yourself, use proper equipment.

OK, I just want to address the "injury" claim (since I agree with the
other aspects).  If we review the bidding thus far, we have the tank
connected to the FROG with fittings that can withstand 800PSI.  Fine.  Now
we have the FROG, which is going to allow UP TO 800PSI but stop any flow
above the small bit (22CFH?) needed for welding (but not as low a flow as we 
need for bubbling).  

Situation 1: The FROG is hooked up to the needle valve with some rubber
tubing and clamps that maybe can't stand 800 PSI (for instance in the two
setups of the folks I've forwarded this mail).  If the pressure rises that
high, then the connection to the rubber tube ruptures and CO2 escapes &
drains the tank in an hour.  No harm.  Interestingly, as far as I've heard
from my friends, this has never happened to them, but maybe they are in 
category 2...

Situation 2:  The FROG is connected to the needle valve with strong 
fittings that can stand 800PSI.  The stress is now on the needle valve.  
If it can't deal with it, the needle valve ruptures, spewing the same 
rate of CO2 out, in this case, killing your fish.  Alternatively, the 
needle valve might "hiccup" when enough pressure is put upon it, and 
you'd see (and pretty quickly, I'd guess) fluctuations in the bubble rate.

Nowhere here, however, do I see any injuries on the same order of someone 
sledging the top of a bottle.

Can normal needle valves withstand 800PSI of pressure directly?  I read a
post on here or rec.aquaria once of a guy who didn't use a regulator at
all, but just hooked a needle valve directly to his CO2 bottle.  I 
certainly prefer to have the safety of something inline should the needle 
valve break.  If that is all the FROG does, then that may be a worthwhile 

I would like to gather actual working data from folks who use FROGs, so I 
can update the FAQ.  If you have been using one of these, please e-mail 
me with system details (what else is in the CO2 line from CO2 tank to fish 
tank).  Thanks.

     - Erik

Erik D. Olson					         amazingly, at home
eriko at wrq_com