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Moving from Yeast CO2 to Bottled CO2

I've been doing a lot of doodling and thinking about how I can reduce
variability of my proposed substrate/fertilizer comparison "experiment". One
thing which does bother me is that on the two tanks which I currently have
set up I am using Yeast generated CO2, and as anyone who has ever used this
method would probably agree, the results can vary, batch to batch. So I can
never be certain just how much CO2 is going into each tank (except of course
by doing a CO2 test using my LaMotte test kit). But I'm still left with the
problem of possibly havig one reactor produce lots of CO2 and the other
putting out very little. The results in the individual tanks would them be
affected more by the CO2 variable than by any differences in substrate
and/or fertilizer. Currently, I'm handling this by replacing the Sugar/Yeast
bottles once a week (a lot of work, when I eventually get all four tanks set

I'm considering switching over to bottled CO2, and would like to know how
people with multiple tanks handle this. Do you have multiple CO2 cylinders,
each with a regulator, or can I get one 20 lb. CO2 bottle, use a single
regulator and then bleed the CO2 gas into multiple tanks?

I _assume_ (and please correct me here if I'm wrong) that a brass gang valve
(such as the ones used for regular airline tubing) is not precise enough or
leakproof enough for CO2. Am I wrong here, or would this work???

I further get the impression from both the FAQ's, George Booth's web-site,
and from the info Dave Gromberg has posted (http://www.wcf.com/co2iron/)
that there are basically two types of set-up's, high pressure and low

In high pressure systems, the CO2 gas flows from the bottle at high pressure
through a dual gauge regulator and check valve and then gets fed at
approximately 15 psi to a "sintered glass diffuser", such as those sold by
Dupla, Eheim or ADA. I've learned from Dave's site that in this sort of
set-up a "needle valve" is not needed or used. He recommends that if you
wish to have the second type of set-up, the low pressure system, that you
use a "natural gas regulator" after the usual dual gauge regulator on the
CO2 bottle. Dave further states that this is "untried territory" and

On George Booth's site, he discusses what I assume is a "low pressure"
system, as he employs a needle valve after the regulator, and I think that
George uses the Dupla Reactor "S" (at least in one tank which he has written

I have heard people both recommend and warn against the use of "flowmeters".
Homegrown Hydroponics, a local chain of stores in Ontario has recommended
that this is the easiest way to go but I fear that they may have been
smoking something slightly illegal as I think that a flowmeter would be
better used to deliver CO2 to a crop of tomatoes in a greenhouse than an
aquarium full of fish and plants. On the other hand, George Booth discusses
the use of a "Victor Flow Regulator" and states that while expensive, it
works like a charm. The model number is HRF1425-320.

I'm confused. I'm terribly confused. I don't think I'm dumb, or slow, I'm
just confused. I can understand water chemistry, I can understand lighting,
gee, I've even managed to be able to teach courses in Canadian Income Tax
Regulations. But CO2 injection has me stumped.

I certainly don't want to lay my CO2 bottle down on it's side and get to be
the first person to visit the new International Space Station on an
unscheduled flight.

Humour aside (that was at least an "attempt" at a little levity), how do I
do it? I'm not interested in solenoids (I can see no point in shutting off
the CO2 flow at night) and I won't be going the "fully automatic" route
using a pH controller, due to the abhorrent cost of such systems here in

I just want to have one 20 lb. CO2 cylinder (which I can get locally) and
hook it up in a manner which would allow me to feed CO2 gas EQUALLY into
four separate tanks. I don't really care if I use "sintered glass" diffusers
("high pressure" system)(they aren't that expensive, at least the Eheim
model). I don't mind using 4 separate bubble counters (one per tank) and
doing a bit of fiddling to get an equal input rate in each tank (if I have

Alternatively, I could use individual CO2 reactors within each tank (I have
made one for my main tank using the tube from a gravel washer, a powerhead,
and a handfull of Dupla Minicascades). I asuume that would be a "low
pressure" system. Would I need four separate needle valves to pull this off?
Or is it even possible?

How do people with multiple tanks handle CO2 input? Do those with multiple
aquariums have multiple CO2 setups?

Help! (Please....)

James Purchase