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Proposed CO2 setup for equal addition of CO2 to multiple tanks

Thanks again to everyone who provided input and feedback on my query
regarding equalizing the dosing of CO2 to multiple aquariums. You certainly
are an inventive group.

What follows is a brief summary of the information I received, and my
impression of the input. Again, _please_ feel free to correct me if I have
misunderstood what anyone has suggested. I'm desperately tying to understand
a topic which I have very little prior knowledge of, and I appreciate any
help I can get.

I am also providing some details of other parts of my proposed setup,
hopefully for people who do not understand what I am attempting.

As a preface, please remember that the reason I wish to equalize the CO2
input to each tank is to remove the addition of CO2 as a variable in my
study of commercial substrate/fertilizer systems. I currently have two tanks
up and running, both using Yeast generated CO2 and I have noticed a high
degree of variability in the production of individual Yeast/Sugar mixtures.
Some work great, others just putter along. Each tank looks great (as far as
plant growth is concerned) but there are great flucuations in CO2 content
with time in each tank, depending upon how well the individual Yeast
generators are working. Over the course of the study, it is possible that
the effects would average out, but I have no confidence that this averaging
would take place and I would like to have the issue settled once and for
all. The only thing I have really learned to this point is how much I
initially underestimated what I'm attempting to study.

Eric Olson very kindly sent me photographs and a detailed explanation of his
CO2 setup which feeds multiple tanks. However, Eric's setup is not
necessarily designed (as I understand it) to provide an "equal" amount of
CO2 to each tank. He uses individual ARO NO-1 Needle Valves on each line.
This would allow him to fine tune (within the limits of the NO-1 valve) the
amount of CO2 which enters each aquarium. For a regular setup, it looks to
me to be very well designed and flexible.

From the various "needle valve" disucssions in the archive and on George
Booth's site, I gather that the NO-1 is now obsolete and has been replaced
by other models. But both the NO-1 and it's similar cost replacements quite
often have problems in holding a setting at the low end of their range,
which is where I gather a CO2 setup for an aquarium would be located. The
Nupro B-4MG2 is described in a number of archived posts as being much more
precise and accurate, albeit more expensive. But since in the design I have
come up with only one Needle valve is used, this increased cost should not
be a problem.

Paul Krombholz told me that during his studies he has determined that
varying amounts of CO2 can have a very large effect on plant growth and that
unless I can manage to get a handle on this variability, there would be
absolutely no way that the effects of different substrate/fertilizers could
be isolated from the effect of the CO2. (This is at least my understanding
of what Paul said - if I'm mistaken Paul, please accept my apology and
correct me.) Paul suggested the use of "capillary tubes" as a possible
method to regulate the amount of CO2 entering each tank.

Paul also stressed the fact that different tanks can, quite naturally, have
different levels of CO2, depending upon such factors as organic content in
the substrate, fish load, food input, etc. Roger Miller made the same
comments and this just reinforces my initial impression that CO2 must be
used for the study. Several of the companies who produce full lines of plant
products, notably Dupla, ADA, Dennerele and Eheim include CO2 injection in
their recommendations and provide specifically designed hardware for this
purpose. But while I'm looking at the major "systems", I'm not attempting to
evaluate how well their CO2 equipment works - I'm focusing on the nutrition
provided by their substrate/fertilizer products.

Dr. Dave suggested that I set up the system as a closed "loop", wherein an
equal pressure of CO2 is provided to each tank. He described a system which
he used during his PhD studies using just such a closed loop with air pumps
to provide equal aeration to multiple tanks. Several people mentioned in
archived postings of the APD that pressure and flow are not the same thing,
but to my mind (again - if I'm mistaken, please jump in!), if I am using
aquariums of equal size and reactors of the same type and size within each
tank, an equal pressure of CO2 _should_ provide an equal amount of the gas
to each tank. The diagram I have included with this posting is based upon my
interpretation of this idea.

My only query here is the fact that the tanks will be on differnt levels (2
tanks side by side over 2 tanks side by side). Would the height difference
change the amount of CO2 which would flow to the tanks of different levels,
or would equalizing the tubing length to each tank comensate for this
difference in height???

For the individual Reactors within each tank, I suppose I could use either
sintered glass diffusors (Christopher Coleman did a great review of the ADA
Pollen Glass and the Eheim diffuser which is in the archives), or make
counter current reaction chambers (similar in effect to the Dupla Reactor
"S") powered by indivdual power heads. I have such a home made unit in my
large show tank and it works very well. Any suggestions as to preference of
one over the other would be appreciated. Christopher, do you think that the
Eheim unit could adequately supple CO2 to a 30 gallon tank?

Both Roger Miller and Steve Pushak reminded me that the omission of
artifically supplied CO2 and a lack of live fish in the tanks during the
study would mean that certain nutrients (Carbon, Nitrogen and Phosphorous
being possibly the most important) would have to be supplied in some other
fashion. Steve made several suggestions regarding how this could be
rectified. But when I go back to the original idea which sparked my interest
in this, I have to keep in mind that most "plant systems" are designed for
"fish tanks".

The presence of fish, the food they eat and their waste products are
probably taken into consideration when the formulation of the aquatic plant
fertilizers is determined. I see no mention in any of Dupla's or Dennerele's
literature which indicates that their systems would work as well without
fish as they do with fish present. Ergo, the fish are back in. To reduce
flucuations from this area, I suppose I am going to have to have the same
number and mix of fish in each tank and make sure that I accurately measure
the food input into each tank and ensure that it is the same for each tank.

Similarly for plant number and mixture, at least for initial planting and
subsequent introductions, I shall use the same number and species mix in
each tank. It is possible that certain plant species will react differently
in each tank (hopefully, in response to the different
fertilizer/substrates), but this would be one of the things I am studying.

Lighting for each tank will be identical - 4 40W F40C50 Chroma 50's over
each set of tanks, suspended an equal distance over the top of the tanks and
each 30 Gallon tank will receive approximately 2.4 W/gal of light. There is
room in the design, and over the tops of the new tanks which I have ordered
(4 - 24" X 18" X 18" all glass tanks) to place another twin tube fixture
(for a total of 240 W over each tank pair, bringing the lighting level to
3.6 W/gal, should I notice any need to crank the light that high. Fixtures
used will be standard twin tube fluorescent shop lights.

I feel confident that by using TFC R/O water as my sole source of water for
this study, and by using commonly available and similar amounts of salts
(Kent R/O Right, CaCO3 tablets and Sodium Bicarbonate) to reconstitute it
and adjust Hardness and Alkalinity, I  am removing any influence of my local
Toronto water. While not everyone resorts to the use of this type/method of
water preparation, it is something which removes the vast differences in
local water variability and which anyone can do.

I hope that the following diagram gets through everyone's e-mail programs
O.K. This is how I _think_ the CO2 subsystem should be set up to accomplish
what I want it to. Again, any input/corrections are welcome. Should you wish
to do so off list so as not to bore those not interested, please do so
(mailto:jpurch at interlog_com).

Proposed Setup to provide Multiple Aquariums with an Equal Amount of CO2:

1      Dual Guage ____ 20# CO2
       Regulator       Cylinder
2      Nupro B-4MG2
       Needle Valve
3       Check Valve
4      Manifold
       "T" Valve #1
5   |<<<<<<<<|
    |        |
    |        |
    |     "T" Valve #2
    |        |
    |        |
6   |        |>>>>>>>>>>>> Check Valve - Bubble Counter
    |        |                                 |
    |        |                              Reactor
    |     "T" Valve #3                      Tank1
    |        |
    |        |
7   |        |>>>>>>>>>>>> Check Valve - Bubble Counter
    |        |                                 |
    |        |                              Reactor
    |     "T" Valve #4                      Tank 2
    |        |
    |        |
8   |        |>>>>>>>>>>>> Check Valve - Bubble Counter
    |        |                                 |
    |        |                              Reactor
    |     "T" Valve #5                      Tank 3
    |        |
    |        |
9   |        |>>>>>>>>>>>> Check Valve - Bubble Counter
    |        |                                 |
10  |<<<<<<<<|                              Reactor
                                            Tank 4


Check Valve (3) is there to protect the Needle Valve,
should anything downstream fail.

One arm of "T" Valve #1 (5) is connected to one arm of
"T" Valve #5 (10), forming an "equal pressure loop".

Check Valves (6,7,8,9) are to ensure that no water
enters the "T" Valves.

Individual Bubble Counters (6,7,8,9) are to ensure
an equal volume of CO2 enters the individual Reactors
in each Tank (sort of a visual check and confirmation for me).

*** The major difference between this and Eric's setup is the use of only a
single needle valve (his set up uses multiple NO-1's running off the "T"
valves before the Reactors), and the tubing running from "T" Valves #1 and
#5. Eric has suggested that I stick with (if I can get them) Swagelok "T"'s
and their associated compression fittings. I have located several local
suppliers of Swagelok valves (Swagelok's WWW site has lins to local dealers
all over the place). Swagelok is apparently the owner/manufacturer of Nupro

Sorry for the length of this post, but I wanted to get all of the details
down in one place for people to be able to comment on. Thanks for your


James Purchase
Toronto, Ontario