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> I would like to hear from people what the differences are between reactors
> and diffusors...(those that release a fine mist of bubbles).
> Do reactors saturate the water more with CO2 than diffusors?

yes, definitely.

> To what extent?

100% dissolution in water, as opposed to the bubbles, many of which escape
out the top of the tank before even dissolving.

So then the con I presume is that it takes more co2 to reach the desired

> Is CO2 that is mixed with water before being released into the aquarium
> stable? Anotherwords does CO2 from a diffusor burn off somehow quicker?
> role does circulation in the tank play?

I don't think that there is any difference between the two methods ONCE
the CO2 is actually dissolved in the water.  The problem is simply that
diffusors let gas escape out the tank before it is dissolved to begin
with, while reactors trap the gas in a sealed chamber until it dissolves
in the water.

I guess what I was getting at was, in a large tank, say over 100 gallons,
would good circulation be needed to carry the dissolved CO2 across the whole

> What are the advantages or disadvantages of either method?

Bottle + Regulator + needle valve + reactor
- -------------------------------------------
PRO can be 100% efficient, fast dissolving, little cleaning required
CON bulky and/or external, requires water flow, bubble counter
May be cheaper, or more expensive... Pro or Con?

Bottle + Reg + Glass diffuser
- -----------------------------
PRO simple, not intrusive in tank, self-contained
CON dumping problem, algae build-up, difficult to adjust, inefficient

Bottle + Reg + powerhead/canister diffusion
- -------------------------------------------
PRO easy, works with existing hardware, no dump problem
CON even less efficient than diffusor

In what way? Is part of the CO2 lost in the filter itself?

inverted bell
- -------------
PRO simple, can be efficient, fairly safe (vents excess out bottom)
CON bulky and ugly, and inefficient RATE of dissolving

Here is my problem: In my 100 gallon aquarium I have had a real problem
keeping a steady rate of CO2. I often get either too much, or too little. I
have been using the Eheim, (is that spelled right?)diffusor. I have a fluval
cannister spray bar set a couple of inches below the waterline. When the
water evaporates to expose the spray bar, obviously I am burning off CO2,
but when the water is full, I cant seem to reach the 20-30 ppm. I am either
somewhere below ten, or high enough to start having sudden deaths of fish.

On at least one occasion the CO2 tank was running near empty, and I suppose
I could have had some dumping, but the main problem seems to be when I try
to raise the CO2 level. I also had the diffusor at one end of the tank which
gets very little circulation. The water surface would develop a milky film
and a layer of bubbles, and then I start losing fish, mostly bottom
dwellers. On Tom Barrs suggestion I moved the diffusor under the spray bar
to throw the CO2 out into the water before it reaches the surface. It has
appeared to help to some extent, but I am afraid to raise the CO2 level, and
I am still at a level that is much too low.

I have purchased a reactor and needle valve in the hope that the flow is
more stable and easier to control, but I havnt had time to hook it up yet.
To make things more difficult, I have a hard time with test kits because I
am partially color blind.

I have taken a few steps: I clean the diffusor every couple of weeks, (a
real pain) I shut off the cannister filter during water changes, and I keep
the tank topped off with the spray bar pointed more down than out to prevent
rapid CO2 depletion. The last major problem happended in less than 24 hours
when I tryed to raise the CO2...when I got home from work I found several
fish belly up and several others dancing in circles and banging their heads
on the glass. I immediately changed 50% of the water and those that werent
already gone were saved, and I then lowered the co2 again by one turn of the
screw. The PSI is just under 15. (When I try and raise it, it jumps up to 20
psi, which seems to be the level that is too much) Where it has stayed ever

Am I correct that a reactor would solve my problem?
Oh BTW, Tom tested my KH for me and said it was around 5 if I remember
correctly. Is that right Tom?

Robert Paul H