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CO2 diffusor

At 03:48 AM 4/11/2000 -0400, Sherlock Wong asked: 
>I bought a Aqua-Medic Membrane CO2 Diffuser 
>If the pressure is higher than 1-2 PSI, alot of big bubbles escape.

Here is the problem.   It is very hard to deliver a RELIABLE pressure of
1-2 psi (stable to +-5%).  The Eheim gets around this by requiring a
pressure in the 10 psi range that can vary by even 20% without a ridiculous
result.  That a regulator can do.   To get 1.3psi, you either need:  a two
stage regulator (possible, but I don't know anyone who has gone to all the
trouble) OR a very high quality flow control valve.   Hoke makes a very
nice "micrometering" valve that is fine for the purpose, but about
$100-150.   Some folks have had good luck with the smaller NuPros, be sure
you specify the correct input and output fittings (most folks will not want
the Swagelok defaults).  The NuPros are definitely worth a try if you like
trying out new things.   
Dave Gomberg, San Francisco            mailto:gomberg at wcf_com
Jobe's Fern and Palm Spikes FREE        http://www.wcf.com/pam