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Experience and CO2 regulation
It is a tragedy that in our culture the value of experience has been
discounted in favor of easy religion and apparent science. I have learned to
trust my experience in any given discipline over both of the other
scriptures. I have been using a $65 dual gauge (NOT dual stage) beer
regulator and a $20 needle valve on a 5 pound CO2 cylinder for 4 years. I've
never killed a single fish because of too much CO2, and I almost always run
my CO2 cylinder empty. The CO2 is run from the needle valve through a
plastic tubing into the intake sieve of a canister filter. I count the
bubble rate (1-2 per second for a 65 gallon tank) in the intake sieve. A $65
regulator (described by others here as rubbish) and an $20 needle valve
(described by others here as totally inadequate). That is all. Nothing else.
No dead fish. No pressure pulses. No dumping. Happy plants. Healthy fish. My
experience. I don't have a clue what model number any of the equipment is,
it doesn't matter, I am only relating actual experience with modestly priced
equipment. I believe that anyone can do the same thing. The regulator MUST
be rated for CO2 pressures (the seller will know) and the needle valve
should have the finest movements you can afford, $20 will work, $40 is
better, after that you are just trying to impress your friends.
What follows is speculation (based on experience) and is therefore subject
to more error. I never claim expert status in any discipline except that of
being me.
My "cheap" needle valve is admittedly difficult to set because even a
delicate finger touch causes a noticeable change in output. I suspect that a
$40 valve would be at least twice as easy to set if the same finger touch
produces a smaller change in output. The more expensive needle valves cost
more because they are machined in a way that allows our finger movements to
produce a finer motion at the actual valve opening. I also suspect that the
needle valve produces a backpressure that helps the regulator maintain its
output pressure setting. From what I can gather from this discussion, the
CO2 designs that have a free flow after the regulator are the systems that
can't maintain a regulated gas flow when the cylinder pressure starts
dropping. I suspect that the regulators cannot cope with a changing pressure
on the high side AND a free flow on the low side because the mechanism
interprets the falling pressure on the high side as a higher demand on the
low side and then "dumps" gas to rectify the demand. This is not really a
pressure pulse, but rather a misinterpretation of changing conditions by the
mechanism.
I don't care if it IS made in Germany, if it kills your fish it is still
defective.
I believe that my earlier comment still stands: Any end-of-tank failure is a
failure of the design of the CO2 delivery system.
That should be worth at least 4 cents........
Tom