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

"floguru" wrote:

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

Question - are you basing your conclusions on guesswork, or have you
actually used 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.

The increasing acidity demonstrates quite clearly that CO2 injection
is working, and achieving the result of CO2 gas being dissolved into
the water.

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

Correct, the bubbles from an air pump leave the tank, and so you're
*not* delivering 33 times more CO2 than needed. Everything I've read
(apart from sales babble) indicates that bubbles from an air pump have
little if any direct effect upon dissolved gasses in the water. In
other words, don't consider air pumps at all when you're contemplating
CO2 injection, as they're totally unrelated.

CO2 injection usually involves a reactor of some sort, be it a simple
bell or a powered chamber. I'm using a Hagen diffuser with DIY,
generally delivering one bubble per second of CO2 gas into the
diffuser. Virtually all of that is dissolved into the water, with only
extremely tiny bubbles occasionally leaving the diffuser.

So, unlike the air pump case you present, the vast majority of the CO2
in my system is being dissolving into the water, and not directly
escaping in the form of bubbles.

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.

Most people doing CO2 injection have, though we work the equation in
the other direction. If you know the water hardness and pH, you can
calculate the CO2 level.

You can find the formula and a handy calculator at Chuck's page:
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

By this formula, my CO2 level without injection was typically about
2.6 ppm. Once I got my CO2 injection working, that level rose to and
stays in the mid-teens. With new DIY bottles, CO2 will on occasion
rise as high as 30ppm (DIY isn't as stable over time as bottled CO2
injection, unfortunately).

So yes, we can and do actually measure an increase in dissolved CO2
when using CO2 injection.


--
www.ericschreiber.com

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

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

No, most definitely not. CO2 injection raises the concentration of
CO2 in the water, greatly increasing plant growth.

Plants on land are exposed to 300 to 500 ppm CO2. The water in our
aquarium contain around 3ppm without CO2 injection, even with
excellent aeration mixing air into the water.



Chuck Gadd
http://www.csd.net/~cgadd/aqua

On Thu, 26 Jun 2003 22:31:51 -0500, Eric Schreiber
wrote:

So yes, we can and do actually measure an increase in dissolved CO2
when using CO2 injection.

Right, and contrary to Dean's incorrect conclusion, the benefit is not
simply an acidic pH. If you lower the pH by softening the water and
adding peat (tannic acid), you get the low pH, but not the increased
CO2 levels, and the plant growth will not improve.

In fact, if you have very hard water, you can have a basic pH (over
7.0) with good CO2 injection. If you have very hard water with a KH
of 20 degrees KH, and you inject CO2 to raise the level to 15ppm, you
will have a pH of 7.6, and you will see the benefit of increased CO2
level in the plant growth, without the acidic pH.


Chuck Gadd
http://www.csd.net/~cgadd/aqua

IMHO, the question should be, "Do you want it to work?":
http://mike-edwardes.members.beeb.net/plant/hitech.html

Mike.
--
Mike Edwardes Tropicals
http://mike-edwardes.members.beeb.net

Using the typical DIY yeast fermentation method of CO2 production, what
level of alcohol diffusion do you get along with the CO2, if any? Seems
like that would also be getting into the tank....

"Eric Schreiber" wrote in message
...
"floguru" wrote:

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

Question - are you basing your conclusions on guesswork, or have you
actually used 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.

The increasing acidity demonstrates quite clearly that CO2 injection
is working, and achieving the result of CO2 gas being dissolved into
the water.

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

Correct, the bubbles from an air pump leave the tank, and so you're
*not* delivering 33 times more CO2 than needed. Everything I've read
(apart from sales babble) indicates that bubbles from an air pump have
little if any direct effect upon dissolved gasses in the water. In
other words, don't consider air pumps at all when you're contemplating
CO2 injection, as they're totally unrelated.

CO2 injection usually involves a reactor of some sort, be it a simple
bell or a powered chamber. I'm using a Hagen diffuser with DIY,
generally delivering one bubble per second of CO2 gas into the
diffuser. Virtually all of that is dissolved into the water, with only
extremely tiny bubbles occasionally leaving the diffuser.

So, unlike the air pump case you present, the vast majority of the CO2
in my system is being dissolving into the water, and not directly
escaping in the form of bubbles.

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.

Most people doing CO2 injection have, though we work the equation in
the other direction. If you know the water hardness and pH, you can
calculate the CO2 level.

You can find the formula and a handy calculator at Chuck's page:
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

By this formula, my CO2 level without injection was typically about
2.6 ppm. Once I got my CO2 injection working, that level rose to and
stays in the mid-teens. With new DIY bottles, CO2 will on occasion
rise as high as 30ppm (DIY isn't as stable over time as bottled CO2
injection, unfortunately).

So yes, we can and do actually measure an increase in dissolved CO2
when using CO2 injection.


--
www.ericschreiber.com

On Fri, 27 Jun 2003 01:28:13 -0500, "Stan"
wrote:

Using the typical DIY yeast fermentation method of CO2 production, what
level of alcohol diffusion do you get along with the CO2, if any? Seems
like that would also be getting into the tank....

As long as the yeast/sugar mixture level is lower than the top of the
bottle, no alcohol gets into the tank.



Chuck Gadd
http://www.csd.net/~cgadd/aqua

I couldn't agree more with Mike! I have two low-tech tanks, a 110 gallon with
about 1 W/gallon of light and a 20-long gallon with about 2 W/gallon. The
plants on the big tank grow like weeds, including some species that are
supposed to "require" high light. If I had to do more prunning it would not
be an enjoyable hobby.
The small tank is just getting started, but it's starting to look nice too.

--
Victor M. Martinez

http://www.che.utexas.edu/~martiv

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.

Xref: 127.0.0.1 rec.aquaria.freshwater.plants:73372

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.

"Paul Davies" wrote in message ...
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
My question is :- are you saying that adding baking soda will give me "free"
CO2?

No, it will only scale up the pH range you need to have a good CO2
level in your tank.

A KH of 50ppm(~3 degrees) needs a pH of about 6.5 or so.
A KH of 350(~20 degrees) needs a pH of 7.3.

Both have the same amount of CO2.

One has more Total carbon(CO2 + HCO3) but both have the same amount of
CO2.

CO2 is what the plant wants.

Just figuire out a way to get more into the tank or increase the
efficiency of the method which you are dissolving the gas.

Regarding trickle filter CO2 losses: it's not the bio tower part, it's
the over flow and splashing etc. Sealed trickle sections should not
lose any CO2 gases. See George's, Steve's and my comments on the APD
regarding this.

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

Regards,
Tom Barr

Thanks Tom for your comments. I've read the threads, and I'll try to make
some changes to the trickle filter to reduce turbulence.

paul davies
" wrote in message
om...
"Paul Davies" wrote in message
...
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
My question is :- are you saying that adding baking soda will give me
"free"
CO2?

No, it will only scale up the pH range you need to have a good CO2
level in your tank.

A KH of 50ppm(~3 degrees) needs a pH of about 6.5 or so.
A KH of 350(~20 degrees) needs a pH of 7.3.

Both have the same amount of CO2.

One has more Total carbon(CO2 + HCO3) but both have the same amount of
CO2.

CO2 is what the plant wants.

Just figuire out a way to get more into the tank or increase the
efficiency of the method which you are dissolving the gas.

Regarding trickle filter CO2 losses: it's not the bio tower part, it's
the over flow and splashing etc. Sealed trickle sections should not
lose any CO2 gases. See George's, Steve's and my comments on the APD
regarding this.

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

Regards,
Tom Barr

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.

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.