CO2 regulator woes

I recently started injecting CO2 from a 5# tank through a single-stage
regulator and a needle valve.  I got the tank reconditioned from a
homebrew store.  I also got an inexpensive (cheap ~$35) regulator from the
same place.  The problem I have is that the regulator freezes (ice forms
on the diaphragm and all the regulating ability is lost) and CO2 is
bubbled full-force into the aquarium.  I have already had one disaster
with this (killed all of the fish in my aquarium).

The folks at the welding supply shop cannot recommend a regulator that
will step the pressure down from the high pressure of the tank to a rate
of a bubble/sec.  I have considered getting a new regulator or turning the
CO2 on in the day, off at night.  Previously, I left the tank on all day,
all night.  Then I would wake up in the middle of the night to hear CO2
blowing full force into the tank.

Has anyone had any experience with this problem?  Might this reg work if
used part-time?  Can anyone recommend a source for a good, reliable

Please Help.

Bryan Vought
bwvought at mailbox_syr.edu