CO2 revelations

CO2 is one of those critical things that aquatic plants folks should really focus on.
I've nagged folks about this for a very long time, and I will likely nag you to the grave.
Complacent experts, newbies, test kit freaks, all of you(and myself included).
Poor CO2 reduces growth and is responsible for nearly 95% of all algae related issues.

Now KH test kit variance is one issue, making a reference standard to compare you KH test to is a very WISE idea to check the accuracy. I've seen many folks have very high CO2 predicted levels, yet fish were fine, but another than has barely 30ppm and the fish are gasping. It cannot be that both are at the same CO2ppm level becaused we would expect to see the same behavior from the fish. Instead we see very wide ranges and impacts on the fish(as well as plants).

So it's much more likely that it is the testing method, rather than anything else.
pH is the best thing as far as accuracy for CO2 measurements using a pH probe and no electrical equipment runnign when the pH is measured(stray current will depress the pH giving false high ppm CO2 levels).

KH test kits have consistency issues (see recent post) and in some places, although rare, non bicarbonate alkalinity exists(recent poster in NM has significant borate alkalinity, desert regions generally).

Addressing this issue by making a reference sample will take care of the KH issue.

The next issue is more interesting for many of of you.
I'd suggested that the venturi DIY reactor I have shown folks on my site is better than any reactor. Well, initially, and perhaps partially true, is the purpging effect of gas build up.
This gas is some O2 and some CO2, but very little "air".

As the gas is expelled, consistently I see better growth, this is not due to O2.
So why would a mist of tiny CO2 bubbles vs dissolved CO2 in solution do better for growing plants?

I addressed the O2 issue simply, I used a diffuser disk for CO2(no O2 gas build up occurs).
But that did not do it __alone__.

I wondered why.

So I placed the diffuser disc near similar current like that produced by the venturi reactor after is starts mistuing the gas out the bottom.

Lo and behold, Bam! Excellent similar growth.
Not the kind of so so growth, but pearling like nothing you have ever seen or perhaps only in a very few well run tanks right after a water change. But I'd not done a water change for a week.
I tried it several times on 4 tanks, same result in each tank. Day after day, intense pearling even with fair good current.

So why would this mist be better than dissolved CO2?

For one thing, it's __pure CO2 gas__, which flows much faster than dissolved CO2 liquid.
The flux rate is much faster with pure CO2 gas than CO2 dissolved in water, so the plants get more CO2 and a more concentrated form.

Some folks may not like the bubbles, some might not like pearling.
But I sure do.

I can say that the venturi effect is one of CO2 now, and not of O2 by using the diffuser disc to rule out O2.

So that just left CO2 and the gas vs dissolved form to consider why one method was better in terms of plant than another.

Both flow and actually having some gas in the tank itself seems to be the key here.
So those disc are not so bad and neither are the venturi reactors.

You can make a purge loop for external reactors by making a hole 1/2 down and running the air line back to the intake for the power head, caniter filter etc, this will not add bubbles but will reduce the gas build up inside the reactor.

The real issue is having gas bubbles in the tank and putting them where the plants are in that form.

I think folks should really consider this/these idea/s and try them.
I've had very intense pearling and have over the entire routine time frame, not just for a day or a few days.

Be careful and watch the fish, CO2 levels when doing this, I've not had any fish issues yet. Make sure there is some surface movement. If you use disc, clean them often(monthly).

For larger tanks, they make 6x1" diffuser stones for about 60$ than can be used set along the bottom back gravel layer so they will not be seen. wwww.aquaticeco.com sells them if interested.

In any event, this notion of having tiny gas bubbles floating around very dissolved CO2 might solve many folk's problems and improve those who seek better growth.

Nitrogen is an essential element, but only 1.5%, vs 40+ % for Carbon, it is very very wise to focus on this if you seek better growth.

With good CO2 levels, even the wimpy plants do very well(Tonia, ES, Eirocauleon) algae dies, pearling as intense as you have ever seen it day after day will occur.

I think the gas bubbles might also be less of an issue for fish since it's not dissolved into solution also.

The nutrients can be addressed easily by doing EI, so you know there's enough, so all that's left to really focus on is the CO2.

So I have been playing around trying to figuire out a good way to reproduce max CO2 without causing issues for fish, and adding enough for the plants.

The CO2 mist + current seems to be the best method.

This can be done with a reactor or a diffuser stone/disc.

Also, folks using spray bars, turn them vertically, next to the intake and place the disc down near this also. This hides the bar, the disc, intake all in one place. Having the spray bar current blowing along the back side the tank wall seems to give good flow characteristics+ near the disc, the water blows out and away from the intake and circles around to the intake.
Since water is being blown directly away from the intake, this gives optimum mixing.
Since water is being blown directly on top of the difusser, all the bubble mist is being blown all over the tank.

The results are easy to see.

The other issue is not to trust the test kits so much until you see the type of pearling like this, no BBA growth etc, slowly and patiently add more CO2 till you get the pearling and good growth. Basically use the test to get close, then tweak(add more) carefully and slowly.
Do not go overboard, do it slowly and observe the plants/fish. Your test may give you high numbers, but if the fish are fine, then it's okay.
Turing off CO2 at night will help add the margin of safety also. We add CO2 for the plants, not to maintain pH. Some leave it 24/7, but mainly out of convenience rather than methodology. With disc, running them at night can cause issues, anyway, you can save 2-3x the gas by not running it at night. We know fish don't care about the pH change.


100% pure gas CO2 is going to supply plants much better than 30ppm in dissolved liquid form.


Regards,
Tom Barr

www.BarrReport.com

http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9775/cid/2339

That is the item I am talking about.


As far as tank siozing, I use and so does ADA, several units on larger tanks, roughly 1 per 50-75 gal or so.

This needs combined with good spray bar flow pointed primarily downward into the plants.

Filters, and power heads etc, work to a degree, but....
They do dissolve more than they push the bubbles around.
If the bubble is ground up inside them consistently, then you get the good CO2 bubble production.

Powereheads seem to produce too many larger bubbles, filters in up holding a large bubble that burps every so often(and produces more waste).

Waste, or bubbles, are broken up into ones that end up on the plants, and those that escape above to the air due to being too large.

Just watch the bubbles and see where they go.

I use the same rate of CO2 in the venturi reactor as I do the disc.
And I get the same result.

I just think folks have not considered the pure 100% gas vs 30ppm of H2O CO2 water.

The waste may not be so bad if you have the right bubble sizing, good flow.

For larger tanks, the above diffuser with a good spray bar set up along the bottom of a tank would do very well.

Regards,
Tom Barr

www.BarrReport.com

Comments,

Dissolved versus undissolved bubbles.............this is where folks are getting boondoggled.
There is a two step process.

1.The initial few minutes/hour/s(typically 1 to 3 hours after the light/CO2 comes on) are mainly dissolving the CO2 into solution.

2.Once a high level builds up, then it becomes much more difficult for the CO2 mist to be dissolved. Chemically: it is more difficult to dissolve a substance against an increasingly larger concentrational gradient.

So in the AM when the lights first come on, the CO2 is poor and the gas rapidly dissolves entirely.

Say we get up to 30ppm dissolved in one hour.
Great, plants are bathed in a rich CO2 solution.
Still the same and works well as what was previously discussed for the last 40 years.

Now, what about the CO2 bubbles at 30ppm?

Are they so quick to dissolve at this level of CO2?

You are adding CO2 to a solution that is already heavily super saturated.
The O2 is at best only mildly super staurated.

After 1-2 hours, the micro bubbles will persist and float around the tank.
This is true for my venturi reactors as well.
That gas build up in the external reactor tubes as well as the internal venrturis are similar later in the day.Think about what that gas might be, I'd suggested it was O2 at one point, the flame test was not conclusive(it put the flame out, suggesting CO2, not O2).

I could see the external reactors perhaps building up O2 later in the day, but what about the internal venturi reactors?

No way, there's nothing to degas O2 in there! This rules out the O2 theory. No other gases are super saturated, thus unable to increase and degas of solution, only O2 and CO2, and CO2 is much higher than O2 relative to ambient in all cases, so this makes sense chemically regarding concentration.

So this means, and I know I'm right(rare), that the CO2 dissolving is greatly reduced later at a stable given CO2 dosing rate in the day after you build up to a certain level. What level? I'd guess about 30ppm.

After you get this into the tank( 30ppm dissolved CO2), then this CO2 micro bubble theory starts to work. You still have 30ppm in the tank, but now you have added pulse of pure CO2 mist on top of that for the plants.

It is not one _or_ the other, they are synergistic, one complement and builds on the other.
My mistake in the past was assuming that the gas in the tube was O2, it's not, it's CO2 excess that's much more difficult to dissolve.

Thinking about the internal venturi reactors has shown that it cannot be O2(why would it degas there just like in the external sealed tubes)?

I tried this without any plants(thus no O2 build up), I had gas build up later in the day, thus reduction in CO2 dissolving at higher ppm levels.
............so there.
I finally figure out why that dang little venturi diffuser worked so good, only took me 12 years ! haha

By using comparative diffusers, reactors etc, I was able to muddle through this.
One by itself would not have answered this question.

30ppm bathes the entire plant, the mist of relatively pure CO2 bathes part of the plant.
Together both drive photosynthesis at a rapid rate that I've observed.

Regards,
Tom Barr

www.BarrReport.com This month's very in depth K+ review article completed.