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CO2 Diffuser


  1. sandpoint CO2 any good..
    by (John Baez) (24 Oct 1994)
  2. [F] Help w/DIY CO2 reactor
    by (John Twilley) (17 Nov 94)
  3. Barret's low consumption CO2 system
    by (Paul Krombholz) (Fri, 28 Jul 1995)
  4. re[2]: Water Flow
    by KB Koh <> (Mon, 14 Aug 95)
  5. CO2 injection
    by Michael Eckardt <> (Mon, 3 Jun 96)
  6. A truely different kind of CO2 reactor
    by Harold Wong <> (Mon, 8 Jul 96)
  7. CO2 diffusion
    by (Karen A Randall) (Tue, 21 May 1996)
  8. Cylindrical CO2 Reactor
    by Marque Crozman <> (Wed, 27 Nov 1996)
  9. article for Krib page
    by raven/ (Dan Perez) (Tue, 16 Dec 1997)
  10. A cheap, simple C02 reactor
    by Alan Silver <alan/> (Wed, 17 Dec 1997)
  11. Power CO2 reactor (DIY)
    by "G. G. Rajendra Kumar" <ggrk/> (Mon, 23 Mar 1998)
  12. CO2 Diffuser
    by "Phil Bixby" <constructive/> (Thu, 9 Apr 1998)
  13. CO2 Diffuser
    by "Phil Bixby" <constructive/> (Thu, 9 Apr 1998)
  14. low pressure CO2 reactor
    by Morten Karlsen <markii/> (Thu, 04 Feb 1999)
  15. Unanswered CO2 question
    by IDMiamiBob/ (Tue, 29 Dec 1998)
  16. CO2 Diffusion
    by "Chuck Lawson" <lawson/> (Sun, 31 Jan 1999)
  17. DIY Co2 Diffuser
    by Augie Eppler <augiee/> (Wed, 26 May 1999)
  18. Efficient, low cost alternative Carbon Dioxide System?
    by "Mike G." <msg/> (Wed, 5 May 1999)
  19. CO2 use and efficiency
    by Dave Gomberg <gomberg/> (Thu, 06 May 1999)
  20. Efficient, low cost alternative Carbon Dioxide System?
    by Hoa Nguyen <nguyenh/> (Thu, 06 May 1999)
  21. CO2 diffuser
    by "Ron Barter" <mistnfrost/> (Fri, 05 Nov 1999)
  22. RE: DIY CO2 reliability
    by "Buckley, Kevin" <kevin.buckley/> (Wed, 26 Apr 2000)
  23. Fun with power tools
    by "Roger S. Miller" <rgrmill/> (Thu, 1 Jun 2000)
  24. Aquatic Plant Digest V4 #809
    by Augie Eppler <augiee/> (Wed, 31 Jan 2001)
  25. Injecting CO2 into the intake of canisters
    by EdTheEdge <edtheedge/> (Fri, 02 Mar 2001)
  26. CO2-Reactor vs Diffuser
    by Scott Hieber <shiebernet/> (23 Aug 00)
  27. CO2 Reactor Choices
    by "Bob" <luna/> (Sat, 27 Jan 2001)

sandpoint CO2 any good..

by (John Baez)
Date: 24 Oct 1994
Newsgroup: rec.aquaria

>     Hello. Just few moments if you would be so kind. :)
>     I am doing research into setting up a 55 gallon planted
> freshwater tank. I want go with CO2 injection for optimum plant
> growth (plant Steriods ;)) and have been tring to see which
> system to use. I have seen the Sandpoint Genesis 1 and 2 in some
> catologs and just wanted to know how well these work and if
> anyone would recomend them, or recomend any other type besides
> them. Thanks for reading. 


If you are going to buy a CO2 system I suggest you go to a carbonics center (look them up in the yellow pages) and buy a low pressure regulator and a 5lb tank. This is
much cheaper (about $80 to $100) than buying the sandpoint and is practically identical.

If you want to automate CO2 injection you'll also need a solenoid valve ($40), a reaction chamber and controller ($250). However, experience tells me that for a freshwater setup you're better off using a bubbling technique.

A good, and cheap, bubbling technique is achieved using a plastic cola bottle, a gang valve, airline tubing and some plastic media to put inside the bottle. Use the airline and the gang valve to inject the CO2 from the bottom of the bottle by making a hole in it and inserting the airline (air tight seal). Using additional airline flow the water into the bottle from the top (usually via gravity). Make another hole at the bottom (about 3/8") to let the water out. Inject CO2 at the rate of about 1 bubble per 

second. After about 24 hours the air gap inside the bottle will be primarily CO2 and will saturate the water flowing through it. Cheap and very efficient.

If you need an 'in tank' model you can make a modified version of the above using 1" PVC or clear tubing and placing it in a corner of your tank. If you need more info drop me a line.



[F] Help w/DIY CO2 reactor

by (John Twilley)
Date: 17 Nov 94
Newsgroup: alt.aquaria,rec.aquaria,sci.aquaria

I apologize in advance for posting to all three groups, but frankly
after reading them, I can see how this particular topic hits all three
topic areas.  Flame me via email if I'm wrong, okay? :-)

All right.  I tried the DIY carbon dioxide thing, but can't quite
visualize how to build a reactor.  What I tried to do is the
following:  take a 8 oz plastic soda container, poke nail holes in the
'bumps' on the bottom and on the base of the slope of the cone near
the top, fill it with marbles (weight and hopeful filter?), stick the
air tube inside, and plunk it in the tank.  Here's ASCII art at its

      surgical tubing ->   ||
   firm plastic straw ->  |  |     N.B.  The 'o's and 'O's
                          |  |           are marbles.
    soda bottle cap ->  |      |
                         ||  ||
                        / |  | \
                       /  |  |  \
                      /OoO|  |oOo\
        nail hole -> /OoOo|  |OoOo\ <- nail hole
                     |oOoO|  |oOoO|
                     |OoOo|  |OoOo|
                     |~~~~|  |~~~~| <- air above, 
                     |OoOo|  |OoOo|    water below
                     |oOoO|  |oOoO|
                     |OoOo|  |OoOo|
                   --|----|  |----|-- <- water above,
                     |OoOo|  |OoOo|      gravel below
                     |oOoO|  |oOoO|
                     |OoOo|  |OoOo|
                     |oOoO|  |oOoO|
                     |OoOo|  |OoOo|

                       ^        ^
                       |        |
                      nail     nail
                      hole     hole

This little gizmo sits on the bottom of my tank, and emits a big
rolling bubble every three or four seconds (the mix is four days old)
but I'm not sure a) how much CO2 is being dissolved, b) if the
reactor's doing any good, or c) what's going on.

Could someone tell me if this is a decent reactor, or if someone has
a decent reactor, could they post a Postscript file or JPG of the
working device in detail?  I have another bottle ready, with nail
holes in the bottom only, to see how that goes.

Thanks a lot -- my plants appreciate it!

Jack Twilley (Nautilus)           | "Shake gently before enjoying."       |  -- Minute Maid Fruit Punch and me | "Subtle as a stomach pump." -- me
GAT c+++ d++ e+ f? g+ h++ !l m n--- p++ r--at- s+/- t--at- u+++(-) w+++ y+

Barret's low consumption CO2 system

by (Paul Krombholz)
Date: Fri, 28 Jul 1995

Diffusion between gas mixtures and water gets a bit complex.  I remember a
lecture I had in college about a diving beetle that dives down with an air
bubble held by waterproof hairs that cover most of its abdomen.  The beetle
does not simply exhaust the oxygen in the air bubble  and then return to
the surface for more air.  As the oxygen content of the bubble drops, more
oxygen starts to diffuse into the air bubble from the water, where the
partial pressure of oxygen is now higher. The beetle would be able stay
down indefinitely, using the air bubble as a gill, except for one thing.
Since the oxygen content of the bubble is lower than that of the water, it
also follows that the nitrogen content of the bubble is higher.  So,
nitrogen diffuses out of the bubble into the water, and the bubble gets
smaller.  Eventually the beetle has to go to the surface because its air
bubble is almost gone.

So, if you have a layer of CO2, trapped under plastic, as CO2 diffuses into
the water, nitrogen and oxygen will diffuse from the water into the bubble.
At equilibrium, the bubble will probably be a good deal smaller than it
was, but it will have the same composition of gasses that are dissolved in
your water.

Paul Krombholz

re[2]: Water Flow

by KB Koh <>
Date: Mon, 14 Aug 95

>From: "John Y. Ching" <>
>Date: Sun, 13 Aug 1995 20:56:52 -0400 (EDT)
>Subject: Re: Water Flow
>I have a Fluval 403 in a 90gal tank. My setup is quite similar to what is
>probably the "standard" setup as pictured in the Fluval manual except the
>spray bars are about 5-6 inches below the waterline to minimize CO2 loss.
>The intake is at the left-back corner and the spray bars are pointed
>lightly downward towards the front of the glass. No problem with the water
>flow as far as I can see.
>Last week I made a DIY CO2 reactor using part of a gravel vacuum tube.
>The reactor is designed so that water flows down the tube containing some
>bio-balls and CO2 is bubbled in from the bottom. Water containing
>dissolved CO2 flows out of the bottom of the reactor. I connected part of
>the waterflow from the Fluval spray bar (drilled a hole in the end-cap) to
>the CO2 reactor and found that the water pressure is dramatically reduced
>out of the spray bar. This may be a solution if you wish to reduce the
>water pressure from the SB.

I have Fluval 303 in my 50gal tank. My intake is on the bottom-left-back corner 
and the return spray bar is about 2" below water line on the right-back. 
the end-cap and fitted an elbow to direct the output to lower part of front 
glass. This greatly reduce the water coming out of spray bar and I have a good 
flow in the front portion glass from right to left. 

Me too connect an air-line tube from spray bar to input of reactor. I made my 
reactor from two clear plastic(?) tit-bits containers. The CO2 come from bottom 
and get trapped in the container. The water with CO2 flow out from bottom. The 
container also work as viewing for bubble counting. Below is the sketch of my 
reactor. I found that I can be without CO2 generator for 2 days and my plants 
still producing O2 bubbles. Give me lots of time to make a new sugar-yeast 
mixture. Don't know how efficient is the reactor but as long as my plants is 
producing bubbles and growing well, I am happy.

                          | |  water from part of spray bar enter here
                          | |
                    +-----+ +-----+
                    |             |
                    |         <------------- CO2 trapped here
                    |             |
                    |             |
                    |  |       |  |
                    |  |       |  |
                    |  |       |  |
                    |  |       |  |
                    |  |     <-------------- use for viewing bubbles,
                    |  |       |  |          some water trapped here.
                    |  |       |  |
                    + -+--+ +--+- +
                          | |    | 
                     |    | |    V 
                     V     CO2 from generator enter here
                    Water+CO2 flow out.


CO2 injection

by Michael Eckardt <>
Date: Mon, 3 Jun 96

Todd March wrote:
>Someone also recommended some "bell" (?) reactor made by Tetra?

I cannot speak for or against the  Tetra bells, but I found the following:
In Bernd Greger's "Aquarium Pflanzen", Kosmos, 1991, I found an
alternative to bubbleing CO2 into a filter. It is similar to the
Tetra diffusion bells but cheaper and more flexible. And you can
DIY. BUT it doesn't give values for soft water.
Greger uses a 3 cm (1 inch would do too) high inverted U-shaped channel 
into which the CO2 is bubbled. The channel is made out of glas or 
plexiglas strips, siliconed together, plus two end caps. The whole 
thing can be attached anywhere in the tank.

The dimensions are calculated as follows:
KH Value    Contact area (cm2)     Channel dimensions (example)
   10  dKH      30 cm2                 10x3 cmxcm
   11           50                     18x3
   12           70                     25x3
   13           90                     30x3
   14          110                     40x3
   15          130                     45x3
plus 20cm2 for each additional 1 degree increase in kH.
These values apply to 100 l (30 USgal) tanks. For a 300l tank, 
multiply by 3.

Although, most of you don't have near the 10 degrees kH, I decided 
to reproduce the whole table anyways for completeness sake.
Unfortunately, he doesn't give values (or a formula) for our low KH
tanks and since I don't use this myself, I leave it up to you
to figure out how much contact area you need. 
I guess that by adding some sort of sliding divider into a 20cm x 1cm 
channel, one could fiddle with the contact area until the pH is at the
desired level.

Three additional notes:
1) By bubbleing the CO2 below the channel into the water, you can then 
easily monitor the output of your yeast system. (natural bubble counter)
2) The channel needs to be "burped" periodically to vent other gases that
accumulate over time.
3) This could be a nice set up for a no filter tank.


A truely different kind of CO2 reactor

by Harold Wong <>
Date: Mon, 8 Jul 96

Grettings all. I would like to share how I inject CO2 into my tank.
Instead of the "cup" method, I inject CO2 (one bubble at a time)
along two 4 feet by 1/2 inch rigid tube. I installed them along
the back wall of my tank shaped like a ">". I then inject CO2 at
the lowest point of the tubes. The facinating part of this setup
is that you get to see the bubble shrink as it is being absorbed
into the water. At some point, the bubble stops shrinking and I just
let it go out into the atmosphere. I believe this "leftover" bubble
is just other gasses. Why? because I've collected this gas before and
let it sit in the tank and it doesn't get smaller while fresh gas from
my CO2 tank is being absorbed as I watch it. This tells me whatever was
being absorbed is all gone.
          \  \
            \ .\
             \  \
              \  \
               \ .\
                \  \ 4 feet tubes
                 \  \
                  \ o\
                   \  \
                    \  \
                     \ o\
                      \  \
                              Leave a gap and let the bubble float into the    
                      /  /      next tube.
                     /  /
                    /  /
                   /O /
                  /  /
                 /  /
                /  /
               /O /
              /  /
             /  /
            / O/
    gap--->  //   
      ------/ Use a smaller tube to inject the CO2. There must be a gap
                between the small tube and the big one.

The next thing I would like to do is to find longer length tubes
so that I can bend it into different shapes. Anybody know where
I can get longer tubes? Thanks.

Let me know if you try it.


CO2 diffusion

by (Karen A Randall)
Date: Tue, 21 May 1996

While pssive diffusion is better than just letting the CO2 bubble 
out of the aquarium, a reaction chamber, where CO2 is actively 
mixed with the water is much more efficient.  This can be done by 
bubbling the water directly into a power or canister filter, but 
that method makes some noise, and it's hard to count bubbles to 
regulate your CO2 flow.  

I use a reaction chamber made of either the fat end of a gravel 
vac, or a small pop bottle with the bottom cut off.  This is 
attached to the outflow of a canister filter.

____________ | Outflow from filter
___       / || \
   \     /  ||  \
    \    |  ||  |
     \   |      | Gravel vac
      |  |  o   | (or bottle with the bottom cut off)
      |  | o   o|
      |  |   o  |
      |  |  o   |
      |  |__|___|
      |     |
      |_____| CO2 line

There is virtually no CO2 lost with this method.  It is all 
completely dissolved as it tumbles around within the chamber.

Karen Randall
Aquatic Gardeners Assoc.
Boston, MA

Cylindrical CO2 Reactor

by Marque Crozman <>
Date: Wed, 27 Nov 1996

Greetings Erik, 

There is a design for a reactor here in Aussie that is cylindrical,
about 2 inches in diameter and about 4 inches long, that attaches to
the output of a pump and achieves CO2 levels in the water of up to
55mg/l - in one pass through the unit (the injected level is dependent
on the flow rate of CO2 into the unit). The big thing is that no
bubbles leave the reactor, all of the CO2 injected is completely
disolved. The unit can be operated on just 5psi and boasts flow rates
of upwards of 30g per minute. They seem to work really well on ponds,
where large amounts of CO2 are needed. The unit works on the principal
of spinning vortexes of water, the vortexes prevent the gas from
escaping and keeps the gas tumbling, ie remains in small bubbles -
doesn't settle out at the top of the chamber.

Marque  APD - ANGFA(NSW) <><

article for Krib page

by raven/ (Dan Perez)
Date: Tue, 16 Dec 1997
To: eriko/

I recently posted this to rec.aquaria.plants, but I thought you could use
it on the Krib page as well.  Kind of a thank-you for all the useful info.

A Simple, Inexpensive CO2 Reactor

By Dan Perez (

I just constructed a do-it-yourself CO2 setup, and I was trying to figure
out the best reactor for my 29-gallon upright tank.  A lot of the designs
seemed complex and bulky,  or dependent on equipment I don't have
(powerheads) and so I sat watching the tubes of my undergravel filter
bubble, when an idea hit me for a very simple but effective reactor.

I made it from leftover parts from another tank I had in storage.  Simply
put, it's an uplift tube from an undergravel filter, but capped at BOTH
ends with the fish excluder/bubble directors that usually are mounted on
the top.

At the bottom, you put a few larger stones so that an airstone (connected
to the CO2 source) sits just above the bottom bubble director cap.  Then
you fill the tube with coarse aquarium gravel up to the 3/4 mark.  Cap the
assembly off with the other bubble director and connect the airstone tubing
to the CO2 source.  Here's a diagram (shortened for ease of viewing):

                  | | -----to CO2 source
               /--| |--\
              /ooo| |ooo\___   o = trapped bubble at top
             |    | |       |
             |    | |       |   top cap/outlet
             |    | |       |
             |    | |       |
             |    | |    ___|
             |=== | | == |
             |    | |    |
             |    | |----------rigid tubing for airstone
             |    | |    |
             |    | |    |
             |ggg | | gg |   g = coarse gravel
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |ggg | | gg |
             |    -at--at--at-    |   -at- = airstone
             |    -at--at--at-    |
             |    -at--at--at-    |
             |===========|___         the larger stones in the bottom
             |               |         cap support the airstone in the tube
             |     larger    |

             |     stones    |  bottom cap/inlet
             |     here      |
             |             __|
             \            /

The gravel traps some of the CO2 that bubbles up, as well as encouraging
bubbles on the rise to dissolve.  I noticed that a sizable bubble of CO2
collected at the very top of the assembly, which was an unexpected bonus.
The assembly promotes water flow (passively, of course) as some of the gas
bubbles to the top.  You can monitor bubble flow in the clear section of
the tube at the top.

What I like about this assembly was its ease of construction, its low cost
(the only thing I didn't have on hand was the rigid tubing and an extra
airstone), and its very slim profile.  Give this one a try!

A cheap, simple C02 reactor

by Alan Silver <alan/>
Date: Wed, 17 Dec 1997
Newsgroup: rec.aquaria.freshwater.plants

Dan Perez <> wrote ...
>I just constructed a do-it-yourself CO2 setup, and I was trying to figure
<details snipped>

A good idea. I did something similar using an old gravel cleaner. This
was even simpler than your design and works well. The gravel cleaner
provided a wide clear tube in which the CO2 collects and through which
the water from the filter falls. 

To follow your excellent example ( 'b's in the diagram below are
supposed to be CO2 bubbles which fill the upper part (or all) of the
chamber) :-

Water from the filter outlet comes in here

         |  |
         |  |
        /    \
       /      \
      /        \
     | -------- |  <-- the "blockage" here is the plate that was used to 
     |bbbbbbbbbb|      filter the rubbish from the water. It now spreads    
     |bbbbbbbbbb|      the water about a bit.
     |   bbbb   |
     |    bbb   |
     |     bbbb----------
     |      bbbb       <-- CO2 goes in here
     |       bb----------
     |          |
     |          |
      CO2 rich water comes out here

This took about five minutes to build and works really well. Hope it's
useful to someone.


NOTE - In order to discourage unsolicited e-mail, the address in the
header may have .ferret added. Please remove this before replying.


Sent By : Alan Silver 

It's not an optical illusion, it just looks like one

Power CO2 reactor (DIY)

by "G. G. Rajendra Kumar" <ggrk/>
Date: Mon, 23 Mar 1998

I use a small/cheap internal power head filter combination unit.

Attach the CO2 feed tubing to the air inlet.
Find an acrylic tube, at least a foot long which fits snugly
over the water outlet spout.
Drill small holes 1.5mm or 1/16" diameter, evenly spaced along a
straight line on the tube.
Seal (air & water tight) one end of this tube.
Attach the other end to the water outlet spout of the power head
so that the holes face downwards.

When the unit is running, the undissolved CO2 will be seen as
bubbles on the top part of the acrylic tube. Water rushing
past the gas will make it dissolve faster than usual.

The advantage of this system is that the amount of CO2
dissolving is limited by the length of the tube and water
quality. If excess CO2 enters the reactor tube will fill
up with gas and bubble out from the bottom. (In my system
the reactor tube overflows at 2 bubbles per minute) You could
increase or decrease the length of the tube to suit your
dissolved CO2 requirements.

Since I had two filter units in the same tank, I Filled the
filter can with small granules of laterite. I assume that the
accelerated water flow over them would release more nutrients
into the water.

Power head
|        |   CO2 in
|        |  ||                               Seal end of tube->
|        |--  ---+---------------------------------------------|
|        |-------+-- ---- --- --- --- --- --- --- --- --- --- -|
+--------+       ^ attach clear      ^ 1.5mm/ 1/16" Holes evenly
|oooooooo|       acrylic tube          along the bottom of tube.
|oooooooo|       to power head
|oooooooo|       outlet (keep tube horizontal)
|oooooooo| Remove sponge etc., fill with small granules of
+--------+ laterite.
Filter can.

- ----------------------------------------------------------------
p.s   Could someone do some tests on the FE levels in the water
      with and without the laterite in the filter? Maybe it does
      not help.. (I don't have and can't find test kits)

     In netscape the above diagram looks terrible. Best viewed under a
viewer.. WIN: Save this file as text and view with notepad.

- --
Bangalore, S. INDIA

CO2 Diffuser

by "Phil Bixby" <constructive/>
Date: Thu, 9 Apr 1998
Newsgroup: rec.aquaria.freshwater.plants

Another idea for the bargain-basement-DIY-CO2 brigade...

I've set up a yeast/sugar CO2 system and had been looking for a suitable
diffuser. My solution:-

Get one of the small, cheap, corner filters (one of the ones with an air
feed that bubbles up through it). Turn it upside down and drill two small
holes about half an inch from what is now the bottom to fix a pair of
suction caps to the two flat faces. Drill some more holes on the curved face
about an inch down from what is now the top, in order to let water circulate
better and also to act as a release for excess CO2. Hook the feed from the
pop bottle to the feed to the filter and that's stage one complete. As CO2
gathers in the upturned filter case it diffuses into the water, but....
..stage two makes it work better. I've got it sited in the back corner under
the spraybar from my external canister filter. The spraybar holes are angled
slightly down in order to reduce surface turbulence. Stage Two: Drill a hole
in the spraybar to take a 1/4" straight plastic connector (as a very tight
push fit), and drill an identical hole in the curved front face of the
diffuser, about half inch down from the existing holes. Fit straight
connectors in the two holes, connect with silicone tube, and the feed from
the spraybar then agitates the water in the diffuser making it much more

I've got nice bubbly plants now. Haven't got around to checking the CO2
level but will do. There are few things more satisfying than fiddling around
on the cheap.

Phil Bixby
York UK.

CO2 Diffuser

by "Phil Bixby" <constructive/>
Date: Thu, 9 Apr 1998
Newsgroup: rec.aquaria.freshwater.plants

Another idea for the bargain-basement-DIY-CO2 brigade...

I've set up a yeast/sugar CO2 system and had been looking for a suitable
diffuser. My solution:-

Get one of the small, cheap, corner filters (one of the ones with an air
feed that bubbles up through it). Turn it upside down and drill two small
holes about half an inch from what is now the bottom to fix a pair of
suction caps to the two flat faces. Drill some more holes on the curved face
about an inch down from what is now the top, in order to let water circulate
better and also to act as a release for excess CO2. Hook the feed from the
pop bottle to the feed to the filter and that's stage one complete. As CO2
gathers in the upturned filter case it diffuses into the water, but....
..stage two makes it work better. I've got it sited in the back corner under
the spraybar from my external canister filter. The spraybar holes are angled
slightly down in order to reduce surface turbulence. Stage Two: Drill a hole
in the spraybar to take a 1/4" straight plastic connector (as a very tight
push fit), and drill an identical hole in the curved front face of the
diffuser, about half inch down from the existing holes. Fit straight
connectors in the two holes, connect with silicone tube, and the feed from
the spraybar then agitates the water in the diffuser making it much more

I've got nice bubbly plants now. Haven't got around to checking the CO2
level but will do. There are few things more satisfying than fiddling around
on the cheap.

Phil Bixby
York UK.

low pressure CO2 reactor

by Morten Karlsen <markii/>
Date: Thu, 04 Feb 1999

I've seen so much going on about reactors lately, so I'm sharing my

         A    B        A: CO2 inlet from regulator or yeast bottle
         ||  ||        B: Water inlet from filter outlet
         ||  ||        Both 4-6 mm hose glued in holes in the cap (C)
         ||  ||
        |      |
        |______|  C
         |    |
        /      \
       /        \
      /          \       
     /            \  D: 0.5 ltr plastic bottle filled with gravel      
     |            |    
     |            |        
     |            |     
     |            |        
     |            |        
     |            |     
     |            |         
     |            |       
     |            |       
     |            |
     |            |           
     | o o o o o o|  E: small holes, Stuff comes out here.....         
The whole thing is submersed. When you start it, it's totally filled
with water, CO2 will eventually fill it up, push water down - excess CO2
escapes the small holes on the bottom.

Reactor efficiency is regulated with water flow

This design is the result of trying both things, CO2 in water (eg on my
canister filters inlet), and water in CO2 - this design. What makes CO2
dissolve in water is contact surface, CO2 consentration and time. This
design at least gives a big contact surface. Efficiency can also be
regulated - probably great for Yeaster's.

I'm currently playing with the idea of putting a more "active" substrate
than gravel in there.. pH is probably really low.....

TIP: With a clear bottle, don't place this thing to close to a light
source - algae will grow in there!

- -- 
Morten Karlsen,

Unanswered CO2 question

by IDMiamiBob/
Date: Tue, 29 Dec 1998

A day or two ago someone asked about a report he'd read that CO2 is best
injected through a reverse UGF.  No one answered, so I thought I'd give my two
siamensis.  I have messed with RUGFs some and can offer some observations.

Most folks on this list (operative word-MOST) prefer not to use UGFs, whether
conventional or backwards. They do have some advantages, and here's one I
hadn't thought of.  By sending the CO2 down under the substrate, it would
maximize the opportunity for the CO2 to be dissolved into the water.

Reverse flow can also offer a couple other advantages:
1)  On George Booth's website, he lists the advantages of substrate heaters.
On the list is the idea that plants can benefit from "warm feet".  Pumping
heated water down under the plate and letting it rise through the gravel can
achieve this.
2)  RUGFs, particularly air-driven ones will provide a current through the
tank without causing CO2-depleting turbulence at the surface.
3)  RUGFs can help keep the upper substrate clean by gently pushing detritus
and other stuff back up for removal by the intake end of the filter, or by a
second cannister or power filter.
4)  I just removed an air-driven RUGF from a thirty-gallon tank.  I was taking
the tank apart to improve its substrate.  When I pulled the tank away from the
wall where it had been sitting for several months, I noticed stains which
appear to be DOCs which the air bubbles adsorbed on their way through the up
tube and then "atomized" when those bubbles popped.  I pulled the filter out
so I can experiment with this serendipitous idea after I finish my 55 gallon
project, growth of which has currently reached a CaSh limited state.  But an
idea worth messing with, even if it takes out only a limited amount of

There are a number of effective ways to get the CO2 to diffuse into the water
before the bubbles escape to the atmosphere.  I suspect this may be the most
effective I have heard of, considering the amount of time the bubbles would be
compelled to spend submerged.  I wouldn't recommend everyone ripping up their
tanks just to get the advantage this would offer.  And each of us should be
free to make individual decisions about their filtration, or even their lack
thereof.  But if you are designing your next tank and want to try this, what
the heck.  Go for it.

Bob Dixon

CO2 Diffusion

by "Chuck Lawson" <lawson/>
Date: Sun, 31 Jan 1999

While we're on the topic of CO2 diffusion, about a month ago, I finally got
around to trying something I had wanted to try for awhile.  Using duct tape,
I sealed the lid of my trickle chamber, (an old Burleson "Gulfstream" unit)
and ran the line from my CO2 regulater into the sump under the trickle
chamber.  There is a foam filter separating this from the rest of the sump,
and the "low water level" of the pump is high enough that there is no open
air area between this area and the open section of the sump, so all of the
CO2 must go into the trickle chamber.  My trickle media is standard orange

My reasoning was that with an abundance of CO2 gas in the trickle chamber,
it can't help but go into solution across all of that surface area.  Any CO2
outgassed remains in the chamber to be redisolved, so none goes to waste.

I've found that adjusting my CO2 flow to around 6 bubbles a second (from the
end of the tube) is sufficient to maintain a CO2 level of around 30 mg/l (pH
6.9 @ 8 dKH) in a reasonably heavily planted open topped tank with a surface
area of 13 1/2 sq. feet (160 gallons, 9' x 18" x ~18").  Dissolved oxygen
remains at saturation, even several hours after lights out.

Before my 3 year old selenoid gave up the ghost (anyone know where to get a
new selenoid for a Hamilton CO2 system?  Hamilton doesn't return my calls),
I did notice some interesting effects regulating the pH, running the CO2 at
a higher rate during the "on" phase  -- the amount of shut-off "lag" was way
higher than it was with a more conventional reactor.  When the target pH was
reached and the CO2 shut off, the pH would continue dropping for another 5
minutes or so, when it stopped virtually "instantly" with a coventional
reactor.  I'm measuring the pH from within the tank, mounted several feet
away from the trickle effluent flow (which might account for some of the
lag).  After the selenoid failed (it failed "open"), I adjusted the flow to
the current level and so far it's reasonably steady, not dropping the pH too
terribly much after lights out, but I'd still like to get back to having a
fully regulated flow; does anyone know if these are fairly universally
replacable?  Will the Aqualine Buschke unit from Pet Warehouse work on this?

So far, I like using the trickle chamber as a diffuser a lot, tho.  No muss,
no fuss, nothing in the tank to hide.

- - Chuck Lawson

DIY Co2 Diffuser

by Augie Eppler <augiee/>
Date: Wed, 26 May 1999


Slip a length of ugf airlift tube over the exhaust of the powerhead, and
attach it to the back wall of the tank using heater clips and suction
cups. If you angle it downward, the bubbles will fight their natural
tendency to rise, and depending on the length of the tubing, very few,
if any bubbles will escape. Works like a charm.

Augie Eppler
Green Cove Springs, Fl.
> Date: Tue, 25 May 1999 15:33:03 PDT
> From: "Joe Anderson" <>
> Subject: DIY CO2 diffuser
> I just checked the Kh-CO2-pH relationship chart at the KRIB and confirmed my
> sneaking suspicion that Im not getting enough CO2 into my tank.  I've heard
> from several people about how to create a diffuser, but most use a cannister
> filter.  I was using both an over-the-back filter (which i've removed as
> advised) and a powerhead with the CO2 input in the venturii (sp?) hole on
> top of the powerhead.  This hasn't seemed to work for me.
> I was wondering if anyone could comment on my soln.?  I plan to use a
> clear-green tube (from a TetraBrilla filter) with the CO2 coming in where
> the air hose is attached. I would cap the top of the tube and attach it to
> the tank with suction cups provided. I would then route the sponge tube to
> the powerhead intake.  The other sponge tube I would leave alone.
> Do you think that this might solve my CO2 problem?  I'm using the 3 cups
> sugar 1tsp baking soda method now and the mixt. seems to bubble adequately
> but my pH has remained constant at 7.6-7.8 with a Kh of 11-12*.  Looking at
> the chart this means I am getting no more CO2 than what is provided by the
> atmosphere above my tank (is this correct)??
> Joe Anderson

Efficient, low cost alternative Carbon Dioxide System?

by "Mike G." <msg/>
Date: Wed, 5 May 1999

Hello All-

I was in my LFS today and picked up a 4 page leaflet named SeaScope.  Inside
I found an article written by Ed Fernandez on a cheaper, more efficient
Carbon Dioxide System for Freshwater Plants.  Now that the credits are out
of the way, here is what it says.  Since I am only using the DIY yeast
method I
don't know how much truth there is to this statement, but he says that "on
top of the carbon dioxide system a typical aquarist will have to also
purchase a 5 lb. bottle of CO2 monthly, as well as a suitable water pump to
circulate water through the unit."  He goes on to say that "a common
complaint is that most of these reactors waste CO2.  After CO2 is injected
into the available units any excess gas bubbles out of the reactors and
escapes at the surface of the water."  He said that "after looking at a lot
of CO2 reactors available, he decided to modify an Aquarium Systems Visi-Jet
PS-100 protein skimmer into a reactor. "  He found that minimal
modifications to the unit eliminated many of the previously mentioned
problems.  It states that the retail cost of a Visi-Jet protein skimmer is
about $50, including the necessary modifications.  I found Visi-Jets in That
Fish Place catalog for $28.99.  He did say that it was about $50 WITH the
necessary modifications though.  The article goes on and says that the
unit diassembles easily for cleaning, and requires no adjustments.  The pump
and reactor are one preassembled unit that hangs inside the tank.  The CO2
enters through the pump and saturates the water with very fine bubbles.
Black plastic netting in the reactor tube traps larger bubbles.  Excess gas
that accumulates in the top of the reactor tube is recycled to the pump by
means of a small flexible air tube.  The CO2-enriched water exits through
the bottom of the reactor, and none of the CO2 is wasted.  The Visi-Jet
reactor is controlled by an Aqua-Medic pH controller set on the maximum
setting of 7.0.  A solenoid valve turns the gas on and off, and the flow is
regulated by a needle valve on the cylinder.

Anyway, there is a diagram included on the page to explain all this, but I'd
have a hard time drawing that here.  Since I've never used a Visi-Jet
protein skimmer (and only know what they look like from the picture in the
That Fish Place catalog) I still have a hard time visualizing and
understanding the total concept.  Maybe someone who has experience with this
particular protein skimmer and CO2 injection in general can understand what
is being written without seeing the diagram and would like to comment and
explain to the rest of us if this is indeed an efficient, low cost
alternative for CO2 injection.

If there is nobody that understands, but has an interest in this, I would be
happy to mail you a copy of the article for personal inspection.  Then maybe
you will understand and can explain it to the rest of us here.

Contact me offlist if necessary.


Mike G. (in SW Louisiana where the humidity is getting high!)

CO2 use and efficiency

by Dave Gomberg <gomberg/>
Date: Thu, 06 May 1999

At 03:48 AM 5/6/99 -0400, Mike G asks:
>I found an article written by Ed Fernandez ....  he says that "on
>top of the carbon dioxide system a typical aquarist will have to also
>purchase a 5 lb. bottle of CO2 monthly, as well as a suitable water pump to
>circulate water through the unit."  He goes on to say that "a common
>complaint is that most of these reactors waste CO2.  

Well, almost everything he says above is wrong, so I would discount the
rest of what he says.   Specifically:

1.  If you are going thru 5# a month you should  have a 20# bottle, they
cost almost the same to refill.

2.  I use less than one pound per month in my 50 gallon with waste.

3.  I do not have a water pump to circulate water thru "the unit", by which
I assume he is referring to a conventional reactor.  I do use a ugf, but I
use an Eheim diffusor to pass the CO2 to the water.  See my web page below
for details.

4.  I don't complain about wasted CO2, nor have I ever heard anyone who has
measured the waste complain.  My system dissolves about 90%.  If I could
avoid waste entirely, my CO2 cost would plummet from the current $.40 per
month to only $.36 per month.   You may have figured out by now that I
prefer to spend my time working out how to keep air in my tires and avoid
that expensive $.25 pump fee instead of optimizing my CO2 use to save four
cents per month.

Once you have seen the Eheim in action, you will appreciate just what a
fine job they have done.  The bad news is that the sintered glass disk
costs almost as much as a whole new unit, so don't plan on getting a spare
disk, get a spare unit.

Feel free to post any additional questions.

- --
Dave Gomberg, San Francisco  
- -----------------------------------------------------------------

Efficient, low cost alternative Carbon Dioxide System?

by Hoa Nguyen <nguyenh/>
Date: Thu, 06 May 1999

At 03:48 AM 5/6/99 -0400, you wrote:
>Date: Wed, 5 May 1999 22:28:59 -0500
>From: "Mike G." <>
>Subject: Efficient, low cost alternative Carbon Dioxide System?
>he says that "on
>top of the carbon dioxide system a typical aquarist will have to also
>purchase a 5 lb. bottle of CO2 monthly,

I guess I'm not typical, since my 2.5 lb bottle has lasted 10 months and
still going.


Hoa G. Nguyen
Freshwater Planted Aquarium:

CO2 diffuser

by "Ron Barter" <mistnfrost/>
Date: Fri, 05 Nov 1999

>Date: Thu, 4 Nov 1999 04:23:34 -0500
>From: "Bob" <>
>Subject: Re: CO2 diffuser
>Sherlock Wong wrote:
>>Has anybody used the new glass CO2 diffuser that Pet Warehouse
>>is selling? It looks just like Amano Pollen glass.


>So far the Coralife wooden diffuser (I
>believe it is lime wood) wins hands down! It has been putting out extremely
>fine bubbles for 4 weeks now with no apparent change in bubble size. Other
>brands of wood airstones may work as well, but that is what the LFS sells
>near me.


The "lime wood" you are refering to is, I'm pretty sure, known more commonly
in America as basswood, Tilia americana. It is favoured by carvers for it's
light weight and the fine textured grain that allows it to hold fine details
when carved. This fine pore structure also produces the fine bubbles we
prefer for the diffusion of CO2 in our aquariiums.

I make my own diffusers from pieces of basswood 3/4" thick by about 3-4"
wide. If you saw 3/4" slices from the board, you can easily get a dozen
diffusers from a foot long piece of wood. The exposed end-grain should be
visible along the length of two edges when you are done... this is where
your fine bubbles will come from. I bore an 11/64 into the 3/4" square end,
making sure to stop drilling short of the oppossite end, and insert a
plastic air line splice half way into the block, sealed with a couple drops
of cyanoacrylate glue (Crazy Glue). I suppose you could also use silicone.
Let the glue dry and your'e all set.

At about $2.50 a board foot, a piece of basswood 3/4" x 3" x 12" would cost
about 83 cents, you can probably get a scrap free if you know a woodworker
or carver. And if one diffuser plugs up, you won't feel too bad about
tossing it and using a fresh one.

Ron Barter
Perth, Ontario 

RE: DIY CO2 reliability

by "Buckley, Kevin" <kevin.buckley/>
Date: Wed, 26 Apr 2000

Someone said:

"Ryan, for the cost of a "good" pH meter, you would be able to get a
perfectly sound CO2 regulator and pressurised gas system. You can forget
about ever being able to reliably hit a specific pH with a DIY yeast
reactor. The output is too variable."

- --------------------------------------------------

I recently started to play with DIY CO2 &, after a number of attempts to
build reliable CO2 reactors I settled on the following approach which
maintains the tank CO2 at a level independent of the amount of CO2 gas being
produced by the fermenter.

Find a box of some kind that has a clear plastic lid (so you can see the
water level in it when it's submerged) in the form of an 'enclosure' (i.e.
when it's upside down, submerged in the tank, you can bubble CO2 up into
it).  See below for dimension info.

Keep the lid & discard the box!

Drill a couple of holes in the top of the lid so that you can push some soft
plastic suckers through & still get a gas tight seal as below (sorry of your
font screws up the diagram):

      \        /                                     \         /
       \------/                                       \-------/
 I                                                                  I
 I                                                                  I

Stick it under the cover glass so that the underside of the box is below the
water surface & in a position such that the outflow from the filter (or a
powerhead) flows past it (my tank has a glass 'lip' that runs all around the
edges so I put it under that, at the back).

Run an airline from the CO2 fermenter under the water, along the back of the
tank, & arrange for the CO2 to bubble up into the box (when you submerge the
box for the first time let all of the air escape so that its just full of

Use a fermenter that significantly oversupplies CO2 (I use 2 x 1 gallon
glass 'demijohns', available cheaply in the UK for home winemaking, joined
with an airline 'T' piece.  I change each one every 4 - 5 weeks but around 2
- - 3 weeks apart so that there is always a very active fermenter running).
Once the box is full of CO2 any additional CO2 overflows (underflows?) &
escapes as gas at the surface.  The CO2 content of the tank water is
determined only by the submerged surface area of the box, the rate of water
flow past the underside box & the rate at which CO2 escapes from the tank
elsewhere due to surface agitation, air-stones etc.  It's unrelated to the
rate at which the fermenter produces CO2 (providing that you are always

Initially I tried the lid off a box of emergency auto bulbs that I had in
the garage (about 14cm x 9cm) - this gave about 45ppm CO2 in my 55g tank
(next to the venturi outflow of a Fluval 404).  I then tried the lid off a
box of push pins (about 7cm x 6cm) this gave about 10ppm.  Finally I settled
with the lid off the box containing a $2 'Paper-Mate' biro (about 17cm x
4cm) which gives about 18ppm.

Hope this is useful!

Regards, Kevin

Fun with power tools

by "Roger S. Miller" <rgrmill/>
Date: Thu, 1 Jun 2000


For some time now I have provided CO2 to my tanks by feeding
yeast-generated CO2 into the inlet of power heads.  The power heads do a
fine job of breaking up the bubbles. In the small tanks where there's not
much distance between the powerhead outlet and the water surface there's
no evident problem.

In my larger tank, where the powerhead outlet is directed through a spray
bar of sorts pointed at a slight downward angle, there is a problem.  The
tiny bubbles coming from the power head don't dissolve, and they create a
cloud of bubbles all over the tank.  The problem is especially bad in the
evening when the plants are really bubbling.  I think what happens is that
when the incoming CO2 hits the pump, the pump not only smashes up the
bubble, but low pressures inside the pump also promotes rapid exsolution
of nitrogen and oxygen from the water into the CO2 bubbles, which keeps
them from dissolving completely. The same thing probably happens in the
other tanks, but in those cases, the bubbles hit the surface fast enough
that I don't notice a problem.

Here's where the power tools come in.  I built a simple CO2 reactor to fix
the problem.  I don't know that there's anything special about the reactor
- -- there might be a half dozen similar designs out there -- but this one
worked pretty well so I thought I'd describe it.

The idea is to create a strong vortex inside a small length of pipe, and
to bubble CO2 into the middle of the vortex.  Being light, the CO2 bubbles
tend to stay in the middle of the vortex until they dissolve.

It consists of a length (I used about 9 inches) of 1 1/2" schedule 40 PVC,
capped at each end, an inlet in the side of the pipe near one end and an
outlet in the side of the pipe at the other end, both arranged so that the
flow through the inlet or outlet is tangent to the inside surface of the

The end caps are standard PVC fittings, cut down so that they seat firmly
against the end of the pipe with only about 1/2" of overlap on the side of
the pipe. I drilled a small hole in one end cap and friction-fit a small
length of rigid plastic airline into the hole.  The CO2 feeds into that
line. The inlets and outlets are tubing barbs cut from a 1/2" PVC elbow.  
All of the PVC parts glue together with PVC cement.

The main problem is to get holes drilled into the pipe that are large
enough to fit the tubing barbs, and at a very low angle to the inside wall
of the pipe so that there is minimal impact between inflowing and
outflowing water and the side of the pipe.  Once the tubing barbs are
glued into place the projections inside the pipe need to be cut down so
the inner wall of the pipe is smooth.  Dremel tools are great for this

The whole layout looks something like this from the side:

             CO2 in
          _|      |
   inlet  _)      |
           |  S   |
           |  w   |
           |  i   |         
           |  r   |
           |  l   |_
           |      (_outlet
           |      |

and from the top, like this:

       ____ ****_____
  inlet___**    **___outlet
         *    0   *
         * CO2 in *
          **    **

The reactor needs to be mounted vertically with a powerhead connected to
the inlet, and a CO2 line connected to the CO2 inlet.  Both inlets are at
the top and the outlet is at the bottom.

The first one I made just as shown and set up to use inside the aquarium.
It works very well, but it's fairly obvious inside the tank.  I'm making
the second one to hang outside the tank.  It differs from this design
mostly in that the joints are all sealed with silicon.

The parts cost a couple dollars.  It took about an hour to cut the pieces,
grind the ends smooth and square and to fit all the pieces.  It wouldn't
take much time at all if (unlike me) you actually cut all the parts square
to start with.  Curing the glue takes a little longer.

If the flow through the pipe is too fast, or not tangent to the side of
the pipe at the inlet and outlet then you won't get a good vortex inside
the pipe and CO2 will just flush through without much time to dissolve.  
The longer the pipe, the longer the gas will have to dissolve.  
Similarly, a larger diameter pipe should provide the gas longer to
dissolve and might accomodate higher flow rates.  Also, the inlet and
outlet can be directed off in different directions.  For internal
installations it might be better to have them at 90 degrees to each other.  
In an external installation it might be better to have them at 180 degrees
to each other.

Roger Miller

P.S.  I managed to get one of the plecos out by putting a piece of
zucchini inside a pint jar and leaving it over night.  The little guy was
feeding on the zucchini when I got up in the morning.  I grabbed the jar
and moved him to another tank.  One down, one to go.

Aquatic Plant Digest V4 #809

by Augie Eppler <augiee/>
Date: Wed, 31 Jan 2001

Chris Schmelzer Wrote: 

> I don't understand how the canister diffusion technique is LESS efficient
> than a diffusor... If you really think about it, it is actually MORE
> efficient and probably the same as a reactor (at least in my setup).. I
> bubble my CO2 (pressurized, regulator, needle valve, bubble counter, then
> into the intake of my Eheim) and I RARELY get a belch from my spray bar
> (submerged).

> What does this mean?  Almost ALL the CO2 put into the Eheim ends up in the
> water, which equates to close to 100% efficiency, MUCH better than a
> diffusor in which a significant percentage of bubbles make it to the
> surface undissolved...

What size is your tank Chris? If I remember correctly, the original
poster had a 100 gallon. IME, using a canister filter as a reactor works
fine on tanks up to 55 gallons. When I moved up to a 125 gallon, with a
corresponding move up in filter size, the filter couldn't handle the
increased amount of CO2. It would either burp on a regular basis, or
"vapor lock" and lose prime. Some people on the list, myself included,
shoot for a reduction in ph of .6. Every time I build a new reactor, or
tweak an existing one, I have to reduce the bubble rate to maintain the
.6 drop. To me, that is the true indication of efficiency, the same drop
in ph using less CO2. And as usual, YMMV.

Augie Eppler
Green Cove Springs, Fl

Injecting CO2 into the intake of canisters

by EdTheEdge <edtheedge/>
Date: Fri, 02 Mar 2001

> ------------------------------
> Date: Thu, 1 Mar 2001 10:10:34 EST
> From:
> Subject: Re: Injecting CO2 into the intake of canisters
> > is injecting bubbles of c02 into cannister filter intakes bad for the
> >  cannister.  Surely the pinging and small pockets of c02 cant be good for
> the
> >  motor or impellor ?
> All I can tell you is from personal experience, and that I've injected CO2 as
> you describe into both canisters and power filters, and have never noticed
> even the slightest evidence of damage of any sort to the impeller blades.
> Eheim canisters seem to be better suited to CO2 injection because the motor
> is located after the media.  With Fluval canisters, a vigorous CO2 flow can
> be noisy, and can occasionally cause vaporlock of the impeller, stopping
> water flow.
> ------------------------------

 I have three Eheim Eccos and they do not take too kindly to having CO2 injected
into them.  One actually seized up and got extremely hot due to vapor lock.  This
filter was damaged to the point that it had to be replaced.  The other two would
get the "rattles" quite frequently.  I have since ceased injecting CO2 via my



CO2-Reactor vs Diffuser

by Scott Hieber <shiebernet/>
Date: 23 Aug 00
To: erik/

I can't remember if I sent this to you or not but I was surprised at the
differences in results. 

Experience with A Glass-disk CO2 Diffuser and Tube-type Mixing Chamber

Summary of CO2 Injection Rates for Equal Absorption Levels

Arranged by Method                         Bubble rate
Eheim Diffuser at Bottom of Tank           180/minute	

Eheim Diffuser at Bottom of Tank & 
 Directly in line with Powerhead Outflow    80/min	

Gravel Tube Mixing Chamber                  45/min

I added 150 watts of VHO fluorescent lamps (URI Aquasun) to a  29-Gallon tank
and started injecting CO2.  The table above summarizes the absorption results
with three different methods of injection.

This tank had been established for about 6 months.  It was not originally
intended as a planted tank and had two biowheels, the space-saving alternative
to trickle filters.  The biowheels promote gas exchange, very good for
oxygenating the water and encouraging  biofiltration but probably
contraindicated for CO2 injection (in comes the bad air, out goes the good). 
But I decided to leave them on to see if I could get reasonably good results. 
I had read ( that CO2
injection can work on tanks with trickle filters if the drip chamber is
reasonably well sealed – the atmosphere in the chamber becomes CO2-enriched
which limits the mount of CO2 escaping from the water.  So, as a temporary
measure, I wrapped the biowheel boxes with Reynolds Plastic Wrap.  If that
worked, I could devise a more permanent “wrapper” later.   This is essentially
an enclosed tank except for the openings necessary for the biowheels returns,
and heater and powerhead cords.

I first installed an Eheim CO2 diffuser, placing it against one side panel at
the top of the substrate.  The Eheim is really just an expensive, very fine
grain glass air-stone, with a bubble(counter) chamber on the bottom and it
comes with a back-flow check valve.  For about twenty bucks, it’s a relatively
inexpensive package.  And Eheim canister filters work so reliably, I figured
this product was a safe bet too.

The water in my area is very soft and near neutral – GH & KH about 1-2, pH
about 7.2.  I pushed the KH to 5 with sodium bicarbonate and started the CO2
injection, aiming for a level of 15ppm.  I measured KH and pH, every few hours
the first day, and once per day thereafter for about a week.  After that, I
measured about once or twice a week.  Since the resolution of pH tests leaves
a wide margin of “error” when computing CO2 levels, I also used a Hach CO2
test for the once per week testing to confirm the KH & pH measurement.  Each
week I changed 20% of the water.

I ended up having to set the CO2 injection rate to 180 bubbles/minute to
achieve a CO2 level of about 15ppm.  Awful results!  I relocated the diffuser
at the substrate directly under a biowheel  powerhead outlet – this outlet was
at a t-joint that diverts some of the powerhead output directly back to the
tank water column, bypassing the biowheel.  I directed the powerhead flow
downward at about 60 degrees so that the bubbles from the diffuser would be
forced downward to circulate around the tank before reaching the surface.  The
powerhead is rated at 170 gallons/hour.  Powerhead ratings generally assume 0"
of head (i.e., no static pressure), so the actual flow rate in use probably
half or about 80-90 gph.  Assuming the t-joint splits the flow roughly in
half, the flow that bypasses the biowheel is about 40-45 gph.  I repeated the
original testing sequence: every few hours; every day; then every week.

Performance was substantially improved. I was able to turn the CO2 rate back
to about 80 bubbles/minute to get a CO2 level of about 15ppm.  Not bad but not
very good either.  Also, it seemed that biofilm would build up on the diffuser
quickly, causing it emit larger, less efficient bubbles.  It needed cleaning
every couple of weeks.

I thought about scrapping the biowheels to improve things, but I didn’t want
to change over the filtration system if I didn’t have to.  I had an old Python
gravel tube which many folks have suggested as DIY reactor
(  With a small flame I curled a
piece of rigid airline tubing into an elongated J-shape -- about 10" long on
one side and about 5" long on the other.  I attached it to the 10" gravel tube
with plastic wire-ties so that it would feed CO2 into the gravel tube from the
bottom, reaching about halfway up the gravel tube.  Then I attached the unit
to the powerhead outlet with a piece of 1/2" tubing.  I hoped the roughly 40
gph powerhead output would be enough to absorb, and carry into the water
column, sufficient amounts of CO2.   In fact, as the top 1/2" or so of the
tube filled with gas, and the water turbulence created a swirl of bubbles in
the tube, the smallest pinpoint bubbles were washed out of the tube, so even
less water flow would be acceptable.  Even with an estimated water flow of
only 40-45 gph, I was able to get a 20ppm CO2 level with a setting of 45
bubbles/min.  Although the gravel tube unit also gets coated with biofilm and
some algae, as did the Eheim diffuser, it happens slowly and does not affect
the performance of the reactor.

If I replaced the biowheels with a canister filter, and placed the canister
outlet well below the tank water surface, I could probably get substantially
better results.  For now, I am happy to have gotten the CO2 rate below 1/sec.

I have just recently set up a 150-gallon planted tank.  I knew that, other
things being equal, this would require larger amounts of CO2 than the
29-gallon tank.  Even though I had two brand new Eheim CO2 diffusers on hand,
guess what I use to inject CO2 into this tank.

S. Hieber

CO2 Reactor Choices

by "Bob" <luna/>
Date: Sat, 27 Jan 2001

> The other Dave G wrote: <selective sniping>
> > I was thinking of trying an inside or outside tank type reactor to  
> > see if this was more efficient. I chose canister injection primarily  
> > to lessen visible equipment inside the tank. I know CO2 is cheap, but 
> > would like to try a more efficient method. Any recommendations for  
> > off the shelf reactors would be appreciated. In-tank or external is  
> > fine. I am going to stay away from DIY at this time.
> Dave,
> A well designed reactor is the most efficient way of getting CO2 into
> solution that I know of. If I were to purchase one, there's only two
> that I would consider. For "in" tank, it would be Tom Barr's. It's all
> clear acrylic and has a couple of features you won't find elsewhere. Our
> boy Dwight was/is selling them (couldn't find it on his web page). For
> "external" use, the only one I know of is made by Hydrologix. Bob
> Buettner has been using one since Nov., and seems to be pleased with it
> (I'm sure he'll chime in).

I'm here....
The Hydrologix Reactor has worked out very well. The only drawback I've found is that the chamber is clear and the place I have to put it gets a little sunlight every to avoid algae build up I've covered it up. I experimented with a lot of different methods over a 2 year period , all of which had different drawbacks. My goal is to be as maintainence free as possible and the HydroLogix has accomplished this goal very nicely for me in the CO2 injection department.
Bob Buettner
>From NW CT
Visit my Freshwater Aquarium site at:

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This page was last updated 17 February 2002