Does CO2 injection work?

On Fri, 27 Jun 2003 00:38:52 UTC, "floguru" wrote:

Forgive me for being controversial but I have drawn the following
conclusions on CO2 injection.

What's wrong with controversy?

There have been a number of replies to this, but I'm going to toss in one
more, concentrating on what really happens to CO2 and carbonates in water,
which is tricky and misleading unless you look at it right, which no
aquarium book I've ever seen tells how to do.

I, of course, have it exactly right. Ahem.


CO2 injection I can only summise has one achievement, to increase the
acidity of an aquarium ...

If you want to hypersaturate your aquarium with CO2 a readily available
solution would be to pour in a bottle of soda water which is just water
hypersaturated with CO2 gas. The only thing is that pH would be extremely
low (never measured it but probably less than 4).

Yes, around 4. Methyl orange, which switches at 3.7, is used as an
indicator when you don't want to see the effects of carbonic acid, but
just stronger acids.

But "hypersaturate" sounds like a misconception of what's happening when
CO2 is injected. See below.


I haven't done the experiments (but I might) having an interest in creating
huge ocean algal blooms in the ocean to suck up some of the excess CO2 we
have injected into our environment.
I would be interested in wheither anyone has actually measured an increase
in dissolved CO2 before and after injection and the corresponding effect on
pH.

It's a challenge that probably no one will meet *directly*. I don't even
know how you'd go about directly measuring dissolved CO2, though I've done
a lot of carbonate measurements, as well as direct measurement of CO2 in
air. Fortunately, you can leave the direct measurements to the chemists
who create tables of chemical constants, and get the dissolved CO2 level
by simple calculations.

The research chemists have worked out the relations of all the forms of
"total carbonate" listed here. (This may be obvious, but bear with me.)

Carbon dioxide, CO2, dissolved in water (what you want, and what our
plants want)

Carbonic acid, H2CO3, in water

Bicarbonate ion, HCO3-, in water

Carbonate ion, CO3--, in water.


All of these are present if any of them is. The _relative_ amounts depend
on the pH in a simple way -- except for the ratio of dissolved CO2 to
H2CO3, which is a constant.

If you know the pH, then you can calculate the relative amounts of all
these forms of carbonate. A simple matter of simultaneous equations. If
you know the total amount, then you can figure out how much of each one.
If you change the pH by a small amount, they all shift.

So this is what we folks with CO2 injection do. Rather, here's what I do
with the water that comes out of my tap; others get different water and
handle it in different ways. I take tap water with a pH in the high 7's
and around 60 parts per million of total carbonate in all forms. I can
calculate how much free CO2 there is, with the available tables; 2 parts
per million or less, and not enough for good plant growth. I bubble CO2
into it till it's down to pH 7; and I add some kind of carbonate till
there are 100 parts per million of total carbonate, and bubble CO2 in to
hold it to pH 7. (A couple of teaspoons of baking soda in a 55-gallon
tank, as it happens.) I look up the amount of free CO2 in the tables,
and wow, I have 14+ ppm of dissolved CO2, which is good for plant growth
(Actually, growth is very good even at 4/5 that level.)

I could do the whole calculation using the good presentation at
http://www.chem.usu.edu/faculty/sbia...ate/Carbonic%2
0Acid.html
But it's easier to let others do it, and read the color-coded chart at
http://www.sfbaaps.com/reference/table_01.shtml
which has total carbonate in units of about 20 ppm, for historical
reasons.

This should make it fairly clear why you don't need soda water to make the
plants grow fast. Very definitely, if you start with very soft water and
bubble lots of CO2 into it to get a high level of dissolved CO2, you're
going to have acid water and unhappy fish, or dead ones; but carbonates
have buffering properties that take care of the problem if you know what
to do.

Now, about that hypersaturation:

Yes, there's too much CO2 in the water this way, far more than will stay
there in contact with the air. And you need contact with the air, because
the fish need oxygen. So, the CO2 slowly leaks out.

Most planted-tank people work hard to keep the air contact down to the
minimum needed to keep the fish population happy; and they dribble CO2
into the tank to replace what goes away. (Some CO2, of course, goes away
by becoming plant tissue; some by leakage.) I admit that I allow lots of
air contact in my system, and I just have to spend more on CO2 to replace
what gets away into the air.

--
Dan Drake

http://www.dandrake.com

Outer Planets update: Uranus, Neptune, Pluto, the check
in the mail, the weapons of mass destruction.

You make some interesting points. Coincidentally, my tap water is, like
yours only 60-70ppm carbonate. In my 100gallon tank, at 2 bubbles per second
CO2, I have difficulty in getting the pH below 7.0, which equates to
10-12ppm CO2. To get to the 20ppm CO2 which the gurus recommend, I would
need a pH of about 6.75. This would need an awful lot of CO2, and I don't
believe my reactor could dissolve at that rate.

My question is :- are you saying that adding baking soda will give me "free"
CO2? If you could possibly do a little more to convince me, I will certainly
give it a try.

I think that my CO2 injection rate is so high because I am using the BioLife
combined trickle and conventional filters, but can't think of a good way to
deactivate the trickle section. Does anyone have any ideas?

Paul Davies


"Dan Drake" wrote in message
news:vhIsdqY67dTD-pn2-RwfEon2rELZt@localhost...
On Fri, 27 Jun 2003 00:38:52 UTC, "floguru" wrote:

Forgive me for being controversial but I have drawn the following
conclusions on CO2 injection.

What's wrong with controversy?

There have been a number of replies to this, but I'm going to toss in one
more, concentrating on what really happens to CO2 and carbonates in water,
which is tricky and misleading unless you look at it right, which no
aquarium book I've ever seen tells how to do.

I, of course, have it exactly right. Ahem.


CO2 injection I can only summise has one achievement, to increase the
acidity of an aquarium ...

If you want to hypersaturate your aquarium with CO2 a readily available
solution would be to pour in a bottle of soda water which is just water
hypersaturated with CO2 gas. The only thing is that pH would be
extremely
low (never measured it but probably less than 4).

Yes, around 4. Methyl orange, which switches at 3.7, is used as an
indicator when you don't want to see the effects of carbonic acid, but
just stronger acids.

But "hypersaturate" sounds like a misconception of what's happening when
CO2 is injected. See below.


I haven't done the experiments (but I might) having an interest in
creating
huge ocean algal blooms in the ocean to suck up some of the excess CO2
we
have injected into our environment.
I would be interested in wheither anyone has actually measured an
increase
in dissolved CO2 before and after injection and the corresponding effect
on
pH.

It's a challenge that probably no one will meet *directly*. I don't even
know how you'd go about directly measuring dissolved CO2, though I've done
a lot of carbonate measurements, as well as direct measurement of CO2 in
air. Fortunately, you can leave the direct measurements to the chemists
who create tables of chemical constants, and get the dissolved CO2 level
by simple calculations.

The research chemists have worked out the relations of all the forms of
"total carbonate" listed here. (This may be obvious, but bear with me.)

Carbon dioxide, CO2, dissolved in water (what you want, and what our
plants want)

Carbonic acid, H2CO3, in water

Bicarbonate ion, HCO3-, in water

Carbonate ion, CO3--, in water.


All of these are present if any of them is. The _relative_ amounts depend
on the pH in a simple way -- except for the ratio of dissolved CO2 to
H2CO3, which is a constant.

If you know the pH, then you can calculate the relative amounts of all
these forms of carbonate. A simple matter of simultaneous equations. If
you know the total amount, then you can figure out how much of each one.
If you change the pH by a small amount, they all shift.

So this is what we folks with CO2 injection do. Rather, here's what I do
with the water that comes out of my tap; others get different water and
handle it in different ways. I take tap water with a pH in the high 7's
and around 60 parts per million of total carbonate in all forms. I can
calculate how much free CO2 there is, with the available tables; 2 parts
per million or less, and not enough for good plant growth. I bubble CO2
into it till it's down to pH 7; and I add some kind of carbonate till
there are 100 parts per million of total carbonate, and bubble CO2 in to
hold it to pH 7. (A couple of teaspoons of baking soda in a 55-gallon
tank, as it happens.) I look up the amount of free CO2 in the tables,
and wow, I have 14+ ppm of dissolved CO2, which is good for plant growth
(Actually, growth is very good even at 4/5 that level.)

I could do the whole calculation using the good presentation at
http://www.chem.usu.edu/faculty/sbia...ate/Carbonic%2
0Acid.html
But it's easier to let others do it, and read the color-coded chart at
http://www.sfbaaps.com/reference/table_01.shtml
which has total carbonate in units of about 20 ppm, for historical
reasons.

This should make it fairly clear why you don't need soda water to make the
plants grow fast. Very definitely, if you start with very soft water and
bubble lots of CO2 into it to get a high level of dissolved CO2, you're
going to have acid water and unhappy fish, or dead ones; but carbonates
have buffering properties that take care of the problem if you know what
to do.

Now, about that hypersaturation:

Yes, there's too much CO2 in the water this way, far more than will stay
there in contact with the air. And you need contact with the air, because
the fish need oxygen. So, the CO2 slowly leaks out.

Most planted-tank people work hard to keep the air contact down to the
minimum needed to keep the fish population happy; and they dribble CO2
into the tank to replace what goes away. (Some CO2, of course, goes away
by becoming plant tissue; some by leakage.) I admit that I allow lots of
air contact in my system, and I just have to spend more on CO2 to replace

what gets away into the air.

--
Dan Drake

http://www.dandrake.com

Outer Planets update: Uranus, Neptune, Pluto, the check
in the mail, the weapons of mass destruction.

On Wed, 2 Jul 2003 19:47:34 UTC, "Paul Davies"
wrote:

You make some interesting points. Coincidentally, my tap water is, like
yours only 60-70ppm carbonate. In my 100gallon tank, at 2 bubbles per second
CO2, I have difficulty in getting the pH below 7.0, which equates to
10-12ppm CO2. To get to the 20ppm CO2 which the gurus recommend, I would
need a pH of about 6.75. This would need an awful lot of CO2, and I don't
believe my reactor could dissolve at that rate.

My question is :- are you saying that adding baking soda will give me "free"
CO2? If you could possibly do a little more to convince me, I will certainly
give it a try.

Tom Barr has already given a good answer, I see. To change the
independent variable from the way he put it: Adding bicarbonate will let
you have more dissolved CO2 at your favorite pH level, like 7.0 or
whatever, than you would with your plain tap water.

It's not free, in that you have to keep pumping CO2 in. First you have to
pump extra CO2 to bring the pH back _down_ where you want it after adding
the bicarb. Then, because your level of free CO2 is higher than before --
that's what you wanted, after all -- the stuff will escape more rapidly,
and you'll have to replace it more rapidly.

The too-rapid escape of CO2 because of too much mixing with air would
raise the pH if you allowed it to; but in practice that means you'll have
to add CO2 a little faster to keep the pH steady.

(This is an exercise in saying the same thing several different ways.
It's the only way I can grasp problems that have several variables that
all affect each other.)


--
Dan Drake

http://www.dandrake.com

Outer Planets update: Uranus, Neptune, Pluto, the check
in the mail, the weapons of mass destruction.

Thanks
Today I tried an experiment. I have 2 Biolife combined trickle/ conventional
filters. At 2 bubbles CO2/sec into my 100gall tank, I was getting a pH of
7.05 (10ppm CO2). I switched off one of the filters for a few hours and the
pH fell to 6.8 (19ppm CO2) at the same bubble rate, so the point has now
been proved.
I have now switched the filter back on, but totally submerged, so that the
trickle section is ineffective.

Paul Davies

"Dan Drake" wrote in message
news:vhIsdqY67dTD-pn2-B03RboG2v7pW@localhost...
On Wed, 2 Jul 2003 19:47:34 UTC, "Paul Davies"
wrote:

You make some interesting points. Coincidentally, my tap water is, like
yours only 60-70ppm carbonate. In my 100gallon tank, at 2 bubbles per
second
CO2, I have difficulty in getting the pH below 7.0, which equates to
10-12ppm CO2. To get to the 20ppm CO2 which the gurus recommend, I would
need a pH of about 6.75. This would need an awful lot of CO2, and I
don't
believe my reactor could dissolve at that rate.

My question is :- are you saying that adding baking soda will give me
"free"
CO2? If you could possibly do a little more to convince me, I will
certainly
give it a try.

Tom Barr has already given a good answer, I see. To change the
independent variable from the way he put it: Adding bicarbonate will let
you have more dissolved CO2 at your favorite pH level, like 7.0 or
whatever, than you would with your plain tap water.

It's not free, in that you have to keep pumping CO2 in. First you have to
pump extra CO2 to bring the pH back _down_ where you want it after adding
the bicarb. Then, because your level of free CO2 is higher than before --
that's what you wanted, after all -- the stuff will escape more rapidly,
and you'll have to replace it more rapidly.

The too-rapid escape of CO2 because of too much mixing with air would
raise the pH if you allowed it to; but in practice that means you'll have
to add CO2 a little faster to keep the pH steady.

(This is an exercise in saying the same thing several different ways.
It's the only way I can grasp problems that have several variables that
all affect each other.)


--
Dan Drake

http://www.dandrake.com

Outer Planets update: Uranus, Neptune, Pluto, the check
in the mail, the weapons of mass destruction.

You need to have a co2 reactor to have 000% dissapation

Want to win a FREE new co2 system or a lighting system check out our
forum for our newest contest coming up

http://www.fish-forums.com

Http://www.aquatic-store.com




On Fri, 27 Jun 2003 10:38:52 +1000, "floguru"
wrote:

Forgive me for being controversial but I have drawn the following
conclusions on CO2 injection.

CO2 injection I can only summise has one achievement, to increase the
acidity of an aquarium and thankfully not as effectively as it could.
CO2 and H2O form H2CO3 (carbonic acid), the same as in rainfall which
naturally is pH 4.5 - 5.5.
If I use an air pump and the % make up of atmospheric air is .036% CO2, a
100 litre per hour air pump (very small) is going to deliver .036 of a litre
of CO2 into my tank every hour its working. That equates to 1 litre a day or
100000 milligrams of CO2 a day. Now aquatic plants only need about 30
milligrams of CO2 per litre of water so I have delivered 33 times more CO2
(based on a 100 litre tank) than they need.
Now here's the kicker. Most of the bubbles go straight to the surface and
take the CO2 with them (air pump or CO2 injection) but at the surface create
agitation which is very effective in capturing and dissolving air into the
water. Without being able to scientifically quantify I would suggest surface
agitation in an aquarium is probably responsible for 50-75% of the dissolved
gases in an aquarium (in oceans and lakes its near 100%). Although the size
of the bubbles will affect the air to water exchange (based on the surface
area size a lot of smaller bubbles will release a lot more gas than fewer
large ones). So a biowheel is doing much more than CO2 injection ever could.
If you want to hypersaturate your aquarium with CO2 a readily available
solution would be to pour in a bottle of soda water which is just water
hypersaturated with CO2 gas. The only thing is that pH would be extremely
low (never measured it but probably less than 4).

I haven't done the experiments (but I might) having an interest in creating
huge ocean algal blooms in the ocean to suck up some of the excess CO2 we
have injected into our environment.
I would be interested in wheither anyone has actually measured an increase
in dissolved CO2 before and after injection and the corresponding effect on
pH.

Dean

However, to achieve "000% dissapation" most any reactor will do. grin

--
Bob Alston

bobalston9 AT aol DOT com
"Fish-Forums.com" wrote in message
...


You need to have a co2 reactor to have 000% dissapation

Want to win a FREE new co2 system or a lighting system check out our
forum for our newest contest coming up

http://www.fish-forums.com

Http://www.aquatic-store.com




On Fri, 27 Jun 2003 10:38:52 +1000, "floguru"
wrote:

Forgive me for being controversial but I have drawn the following
conclusions on CO2 injection.

CO2 injection I can only summise has one achievement, to increase the
acidity of an aquarium and thankfully not as effectively as it could.
CO2 and H2O form H2CO3 (carbonic acid), the same as in rainfall which
naturally is pH 4.5 - 5.5.
If I use an air pump and the % make up of atmospheric air is .036% CO2, a
100 litre per hour air pump (very small) is going to deliver .036 of a
litre
of CO2 into my tank every hour its working. That equates to 1 litre a day
or
100000 milligrams of CO2 a day. Now aquatic plants only need about 30
milligrams of CO2 per litre of water so I have delivered 33 times more CO2
(based on a 100 litre tank) than they need.
Now here's the kicker. Most of the bubbles go straight to the surface and
take the CO2 with them (air pump or CO2 injection) but at the surface
create
agitation which is very effective in capturing and dissolving air into the
water. Without being able to scientifically quantify I would suggest
surface
agitation in an aquarium is probably responsible for 50-75% of the
dissolved
gases in an aquarium (in oceans and lakes its near 100%). Although the
size
of the bubbles will affect the air to water exchange (based on the surface
area size a lot of smaller bubbles will release a lot more gas than fewer
large ones). So a biowheel is doing much more than CO2 injection ever
could.
If you want to hypersaturate your aquarium with CO2 a readily available
solution would be to pour in a bottle of soda water which is just water
hypersaturated with CO2 gas. The only thing is that pH would be extremely
low (never measured it but probably less than 4).

I haven't done the experiments (but I might) having an interest in
creating
huge ocean algal blooms in the ocean to suck up some of the excess CO2 we
have injected into our environment.
I would be interested in wheither anyone has actually measured an increase
in dissolved CO2 before and after injection and the corresponding effect
on
pH.

Dean






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