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Gas Reactors


  1. Good way to lower total hardness / CO2 question
    by (Ross Livingston) (6 Aug 93)
  2. CO2 reactor substitutes (was: salt in freshwater tanks)
    by (Ross Livingston) (Wed, 15 Sep 1993)
  3. Types of CO2 reactors
    by Michael Irlbeck <> (Wed, 17 May 1995)
  4. CO2 reactor
    by George Booth <> (Wed, 17 May 1995)
  5. Plants
    by David Randall <> (17 May 95)
  6. Sandpoint [now Dupla] CO2 Setup
    by George Booth <> (Wed, 17 Jan 1996)
  7. CO2 Reactor Idea
    by dougcs/ (Douglas C. Skokna) (Mon, 10 Feb 1997)
  8. Chunx's CO2 Reactor
    by Chunx <joanna/> (31 Mar 1997)

Good way to lower total hardness / CO2 question

by (Ross Livingston)
Date: 6 Aug 93

Dieter Kreuer ( wrote:

: Another question, about CO2 fertilizing: just for 'testing the waters',
: I would like to bubble some CO2 into the inlet of my Eheim, where it
: should be dissolved quite well. Is that a reasonable alternative
: to a reaction chamber?

That depends on your definition of reasonable.  I recently set up my tank
with CO2.  At first, I just stick the CO2 hose at the inlet to my pump
which returns water from the sump.  It worked pretty well.  That is, the
pH dropped like it should, but I didn't care too much for the little 
CO2 bubbles thrashing around in the tank so I decided to build a reactor.
My end cost was under $10US.  I used an 18" (~45 cm) piece of 3" (1.6 cm)
PVC pipe, two end caps and a pvc 'bulkhead' elbow arrangement for the water
inlet and a small piece of 3/16" (.5 cm).  This sits in my sump and not only
have the bubbles gone away, but I'm using less CO2.  Others have used 2 liter
soda bottles to do the same thing.

:                         And where can I get cheap CO2? Do they sell
: small bottles (one litre) in welding supply stores? Or shall I produce
: CO2 by myself in a bottle with chlorine acid and sodium hydrogen carbo-
: nate? This works quite well, but how can I regulate the flow of gas?
: When I use a hose with a clamp put through the cork of the bottle,
: the pressure will probably pop off the cork. Any suggestions?

I think the general consensus is that it's not worth it to try to make
one's own CO2.  It's 1) too much trouble, 2) more expensive, 3) harder to
regulate, 4) potentially dangerous?  and probably more.  The initial setup
investment is quite high for CO2 but the continual use is not.  Here I found
that the best places to deal with for CO2 are bottling companies.  I found
a new aluminum 20 lbs. tank for $85US, 10 lbs. for $65US and 5 lbs. for $50US.
A new regulator was $50US.  This is the type with two gauges with an adjust-
ment ranging from 0 to 30 psi.  Sorry I don't know how many liters these hold
but for reference, the 20 lbs I got is _around_ 2 ft (60 cm) high and _about_
6 in (15 cm) in diameter.  I went with a larger tank because it costs $10US
to get any tank 'up to and including' this size filled.

Ross Livingston, Unisys Corp.  |  Phone   (801) 594-6217  |  Fax     (801) 594-5518

CO2 reactor substitutes (was: salt in freshwater tanks)

by (Ross Livingston)
Date: Wed, 15 Sep 1993

You should also consider making your own CO2 reactor.  As has been pointed out,
CO2 disolves redily in water.  I made one for a couple bucks from a length of
pvc pipe.  I bought the pipe (3" diameter I believe), a couple end caps, a 
couple pieces of 1" pvc (elbo with 1" threaded female on one side and 1" slip
female on other, 1" threaded male to 1" slip female converter), a couple rubber
o-rings and a length of rigid air-line tubing.  I slapped it all together and
filled it with a couple cents worth of shotgun wadding and it all cost me less
than $5 and took about one hour to assemble.  It disolves CO2 completely at
about any rate I want.  Give it a try.


Ross Livingston, Unisys Corp.  |  Phone   (801) 594-6217  |  Fax     (801) 594-5518
Ross Livingston, Unisys Corp.  |  Phone   (801) 594-6217  |  Fax     (801) 594-5518

Types of CO2 reactors

by Michael Irlbeck <>
Date: Wed, 17 May 1995


The Dupla type S reactor I have is a little different concept. With it, 
the water goes through the CO2, not the CO2 through the water :-)

Imagine it as a plexiglas cylinder, about 25cm in height and 6cm in diameter.
It is filled with the small type of Dupla Bioballs. Actually, a miniature 
trickle filter. Both CO2 and water (from a pump) go in through the top. 
Initially, the cylinder is filled with water  completly, but as more CO2 
gets injected, the water level in the cylinder drops and the water 
trickles through a pure CO2 atmosphere. The water goes out at the bottom 
of the cylinder. Should be faily easy to DIY.
Disadvantage: some gases other than CO2 which might be present in the CO2 
source can't escape and will eventually accumulate if they are not 
readily water soluble. So the cylinder will have to be flushed from time 
to time. Expensive.


CO2 reactor

by George Booth <>
Date: Wed, 17 May 1995

> I looked at some of the reactors and even the fancy ones just had a
> spiral shaped glass tube which allowed bubbles to slowly escape out
> the top to the air. 

This sounds like the AquaLine Bushke (or however it's spelled).
> Do any of the commercial reactors employ more
> active methods for dissolving the CO2?

The Dupla "Reactor S" (or "Reactor $" :-) has a venturi nozzle to mix
the CO2 and water at the top and ceramic "saddles" or mini BioKaskades
to help mix it.  These are very efficient ... and expensive. 


by David Randall <>
Date: 17 May 95

 >>  Subject: CO2 reactor <<


 I use a very simple CO2 reactor that wastes no CO2 in my tanks.  I attach the
fat end of a gravel vac to the outflow of my canister filter so that the water
flows down into the wider tube.  Then I bubble the CO2 in from the bottom with
a piece of rigid airline tubing bent into a "J".  The bubbles are tumbled
within the wide tube, and dissolve completely.  There is no gas buildup in the
top of the chamber, and no bubbles escape.

Sandpoint [now Dupla] CO2 Setup

by George Booth <>
Date: Wed, 17 Jan 1996

> No where do I see a specification for the water flow rate thru the
> Dupla reactor.  Have you read anything specific?

No. I wonder why they even include instructions for all the good they
do.  How are those holes on the side of the Reactor "S" supposed to
regulate the amount of CO2 that gets dissolved?  Of course, compared
to the Aqualine-Bushke CO2 reactor instructions (all in French), the
Dupla instruction pamphlet ain't so bad.  I managed to break the A-B
reactor before I got it working (dropped it on the floor and the hard,
brittle plastic tabs that hold the top on broke off <sigh>).

> The documentation mentions that a pump must be used to achieve a high
> water throughput.  It doesn't, however, mention what high throughput
> means.  I can only guess what rate I'm passing water thru the reactor
> but my guess would be somewhere between 150 and 200 gallons per hour.
> It seems that anything slower causes the reactor to slowly empty of
> water completely and CO2 bubbles escape the reactor through the
> output.  If completely fill the reactor with water, with the current
> water flow rate, the water level drops to around the number 3 mark and
> stays there.

I don't think we're moving that much through the reactor, although
I've never measured it.  I had the same problem you are seeing until I
added a little restriction to the outlet of the reactor.  I took a 2
foot long piece of vinyl hose (5/8" maybe - whatever fits over the
damned metric outlet port) and made a vertical loop in it.  The open
end of the loop is under water in the trickle filter sump and is
positioned near the buckhead fitting so almost all the CO2-laden water
gets sent directly to the aquarium.  The reactor will drain when the
pump is off but will quicky fill with water and stay filled when water
is flowing again.  I can see 1" or so of CO2 bubbles at the top when
the solenoid is on, but no CO2 gets out the bottom.

George in Dreary Colorado Waiting For The Freezing Rain To Turn To
Sleet And Snow By Early Afternoon. 

CO2 Reactor Idea

by dougcs/ (Douglas C. Skokna)
Date: Mon, 10 Feb 1997

About two weeks ago, I posted the idea of using my wet/dry filter as a CO2 

>I'm searching for an idea for a CO2 reactor that will fit within the 
>limitations of my system.  Since my 110 planted tank serves as a room 
>divider, I don't want anything hanging off it and prefer not to have any 
>mechanical equipment in it.  So far, the only mechanical item in it is the 
>return from the W/D filter.
>Currently, I use an inverted "Tuperware" container for CO2 absorption.  It 
>fits in the plenum area of the wet/dry filter.  However. it does not have 
>sufficient surface area to achieve my desired CO2 levels (The highest I 
>have measured is about 8 ppm using a LaMotte test kit.

I have since this posting started using the w/d as the CO2 reactor.

Some of the results:

a.  Start:  using a 6" x 10" inverted Tuperware container for the CO2     
absorbtion with a CO2 rate of ~60 bubbles/min resulted in 6 ppm CO2.

b.  Since I was tinkering with CO2, I added a return sparger to the w/d 
return to achieve subsurface water return instead of a return to the water 
surface.  Consistent with  George Booth's article in the KRIB, the reduced 
surface turbulence increased the CO2 from 6ppm to 8 ppm, at the same 60 
bubbles/min rate.

c.  Next, I started adding the CO2 at the 60 bubble/min rate to the chamber 
of the w/d filter below the water's surface.  After 2, 4 & 8 hours, I 
tested the water.  Results were the same for each test:  8 ppm CO2, and no 
detectable amounts of NH3 or NO2-.

d.  After, 24 hours I increased the CO2 rate to about 100 bubbles / min.  
Testing after 4 hours showed the CO2 increased to 12 ppm and again there 
were no detectable amounts of either ammonia or nitrites.  Tests at 24 & 48 
hours also showed the same results.

IMO, these data indicate:  

1.  The w\d filter is a very good CO2 reactor (I did seal it up before 
starting to add the CO2.)

2.  Harmful levels of ammonia and nitrites did not form indicating that     
    a.  The bio activity in w/d filter is still functioning well or 
    b.  The plants and the bacteria on them and other components of my      
        setup  are adequate for bio filtration and have taken up any        
        diminished w/d bio activity. 

Tank info:

110gal, gH~4 degrees; kH~40 ppm; pH 6.7-6.8, Nitrates-25 ppm and dropping, 
phosphates-0.2 ppm and I hope dropping; & 2-110 watt VHO bulbs


Chunx's CO2 Reactor

by Chunx <joanna/>
Date: 31 Mar 1997
Newsgroup: rec.aquaria.freshwater.plants

Foo <> wrote:
>Chunx wrote:
>> ...
>> Reactor - I built this using a 14" long piece of clear 2" PVC with
>> pipe reducers on each end.  The clear pipe was purchased from a dude
>> on the net for $7.  The reducers were only a couple of bucks.
>Please post a bit more information of the particulars of the 
>reactor. Thanks.

The pipe reducers look like endcaps with 3/4" holes in them, they
fit on the ends of the clear 2" pipe section.  My pump output feeds
into the top of the reactor, water flow down the reactor and out the
bottom.  The bottom has a 3/4" pipe attached which makes U-turn back
up to expel the water into the tank.  A 1/4" hole is drilled in the
middle of the clear pipe through which my tubing from the CO2 cylinder
feeds.  See the drawing.

   Water Flow

      ||    <- 3/4" pipe coming from sump pump
     |__|   <- 2" to 3/4" pipe reducer
     |  |
     |  |
 ___ |  |    <- 2" clear PVC pipe
 -+| |  |
  || | -+~~~ <- hole drilled for CO2 tube
 _|| |  |
 -+| |  |
  || |__|
  || |__|   <- 2" to 3/4" pipe reducer
  ||__||  <- 3/4" pipe, lower U-turn portion is buried in gravel

Up to CO2 <- Plants <- The Krib This page was last updated 29 October 1998