Re:CO2 regulator suggestions

     I use a 20 pound CO2 cylinder, topped off with a regulator (purchased from 
     a local beer-brewing supply for $45) and a NuPro needle valve (mentioned in 
     the FAQ and purchased from a local valve supply for $35).  It's a manual 
     system--no solenoid.  I do not believe it is necessary.
     The regulator has two manometers, one for cylinder pressure and one for 
     output pressure.  The regulator's control valve is not precise enough to 
     consistently produce the 1 bubble/second flow I want, and that is what the 
     needle valve is for.  It has a micrometer-like adjustment that can 
     accurately dole out any flow rate from one bubble/minute to empty the 
     cylinder/minute.  It even has a set screw to prevent my three year old from 
     making unauthorized adjustments.
     I keep the output from the regulator to the needle valve at 30 psi.  Needle 
     valves need a fair amount of incoming pressure (>10-15 psi) to work 
     properly.  Regular airline tubing then runs from the needle valve to my 
     Eheim intake.
     I'm sure the Dupla equipment works just fine, but I cannot imagine a BETTER 
     manual system than mine, especially for the price.