Barr Report - Issue 10 - CO2 - Try this.

Re: Barr Report - Issue 10 - CO2 - Try this.

Hi Ted.

Yes, I tried it again at your request.
I did find this out in terms of observations and I am still working at solving why the tarnations we see what see in each type of CO2 diffusion method, so this does not take a single test, rather several and using a number of methods to answer the issue, even then we still might get at everything.

The test showed 5.8 times slower dissolution for ambient(96% O2
saturation) vs 30ppm of CO2 at 140% O2 saturation(n=3).

That was for the first 3cm of the tube volume with a total of
13cm filled immediately with CO2.

I leave several cm in the top since the efficiency of a reactor decreases greatly near the top.

The next 3cm on the other hand took much longer, virtually no
movement after 30 minutes. I reattached the CO2 back to the
reactor at 1 bub/3sec and the level never went up and grew
slightly by 1.5 cm over the next 2 hours.

By contrast, at ambient levels, the gas rapidly dissolved 6 cm
level in 41 seconds.

That is quite a difference.

You can make what you will of this, but I did the test and that
is what I saw/observed.

Each case had ambient vs 30-35ppm CO2 late in the day as well as
freshly evacuated reactor tubes and CO2 airline/gas line/tubing
in the reactors etc(need to remove all the air).
After fresh CO2 was added, the test time began.

The Disc:
So the CO2 mist that totally dissolves before hitting the
surface would now take instead of 5-10 seconds(we all know CO2
does not dissolve "instantly", be careful not to imply/assume
this) it will now take 25-50 seconds, plenty of time for the
mist to do a lap with decent current. Things are not ideal in
the tank so some will dissolve faster/some slower also.

Yep, CO2 is highly dissolvable in water, I'm not saying it is
not. But it does take __time__ and is influenced by the type of
reactor used, flow rate, bioball design, amibent/super saturated
conditions, and given that CO2 is an acid and KH is a base,
quite unlike any other gas in water. CO2 is also highly
compressible compared to other gases(external reactors do have
some backpressure associated).

Also, if the CO2 mist makes contact in the unstirred layer,
it'll will not dissolved as fast as the open water current(eg on
the left vs floating in the current).

You can also view the smaller CO2 bubbles inside a (very
recently evacuated and refilled with fresh CO2) reactor tube
persisting for longer periods. Add lots of CO2 and see what
happens(do not kill your fish).

This is similar to what you suggested but look inside the reactor at the different times.

If you add more and more CO2, the reactor will not be 100%
efficient and most are not later in the day as CO2 levels build.
You can see them burping tiny gas bubbles.

Same for an internal reactor(simply flip it and crank the CO2
back in).

If I were you, I'd break out the O2 test kits/meters.
That is needed to tell you the rest of the story.

O2 BTW dissolves 92X slower than CO2 at ambient conditions(over
one hour vs 41 seconds for CO2 per unit volume.

But O2 could not have entered and degases so rapidly in the evacuated reactor(no gas could) I would assume. Maybe I am wrong but given what I've done with pure O2, this is seems highly unlikely.

A simple test for that is to run a CO2 reactor with no gas at all added and see if more accumulate(none did).

Okay, so I suppose I could add N2 gas in the tube to make the test more like the CO2. I have no N2 gas available but I'd prefer to simply take the gas sample to the lab and run it through a GC than buy a dozen types of potential gases.

Still, I think we should be able to solve the issue without doing that and spending that $$ for all the gases.

O2 and CO2 are the only gases that seem like they rise and fall daily.
So I would think the focus will only be on these two.

When we turn the CO2 reactor back on early in the morning, we
see the bubble disspear rapidly(seconds), with O2 is takes a
very long time(several hours).

I have gas samples from the reactors, I'll take them to a lab
later next week. I want to rule out the other gases to be sure.

Remember that the 5.8 difference will effect the CO2 reactor's
ability to efficiently dissolve CO2 and the rate of gas being
delivered. At lower CO2 flow rates, the gas does not persist
inside the reactors(you can try that also and see what range of differences you get when you correlate flow rate and bubble size).

Basically as you add more and more CO2 ppm to water, you need
more and more efficiency from the reactor. The CO2 venturi design adds mist as the reactor is overloaded from the gas.

Otherwise any tiny little reactor would be suitable for a 5000
gallon tank as long as it had enough current mixing.

I have a number of things I have still yet to look at on the
issue(but I'm up to my ears in research for the next week). It's
interesting and some things do _appear to conflict_ but that's
what makes it interesting.

It could be a mix of CO2/water vapor/O2.

The other thing that at the end of the day really counts is that
is does quite a number on your plants and makes them grow better
and it's a cheap easy method to add to your existing or new
system.

I will add and modify as to the WHY as I work on it more.
It's not a simple thing even if the method/cost are cheap and the effect is great.


Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Statistics.

The SD is 3ppm CO2. Not much. 30 vs 33ppm should not make a difference.
The O2 on the other hand is 25% higher for the same treatment.

The added 3ppm, lets say 6 ppm for fun, is going to produce 25% more O2 from the plants at 30ppm CO2 ranges(+ or - 3-6ppm)?
The SD is about 6% w/o and 7% with.

I'm assuming, but that does seem like a safe assumption.

Good question and one I was worried about.
So....we can test the CO2 for each tank and then test the O2.
But I've tested at both ends of a tank with good mixing and measured the same CO2 level, yet looking at the CO2 reactor out put, you can see a gradient where the plants pearl more and grow better closer to the reactor.

Now perhaps that is because the plants there get CO2 a few minutes/seconds before the other plants on the far side of the tank.

But with good mixing, that should not be the case.

But as you suggested as well, 30ppm may not be the saturation point for a number of plants. And if that is the case...........then we have learned something quite good.
Good CO2 measurement can address that and O2 meters.

I've done this a few times. But I want to repeat a few things again and look at some different methods to approach the question in a different way.

1. I can use the Gas Chromatograph we have at work for the sample for the reactor gas samples.

2. Does the internal CO2 reactor even degas O2? It accumulates gas later in the day just like the external reactors.
Removing the venturi from these lowers DO and CO2(same for the External sump model).
There are no bioballs in the internal reactor design and it's not under any significant back pressure.

3. Good CO2/O2 measurements. pH and DO meter(I have both) calibrated(I did) and KH measurement(Lamotte and 2x the volume for RedSea).

4. There is no degassing with CO2 disc.

So there a few things still yet to do and the different methods of diffusion seem to give different observational suggestions as to what is going on.

Even still, a real good long look at CO2 in our tanks is a very good idea.
We all have made some past assumptions about CO2, myself and many others, so taking another much more in depth look is a great path.

Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Try this.

Another thing, have folks actually done the mist method with the disc?
I've heard back from about a dozen folks.


Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Try this.

Ted, I redid some internal reactor test.

The reactor does not degas anything(no bioballs etc) when you do not add any CO2 to it, but add plenty of CO2 to 30ppm from another reactor in the same tank.

I tipped it over, released the build up of the the gas in there and added the same level of gas back rapidly by opening the needle valve wide.

This bubble rapidly dissolved, roughly 4 - 5minutes.
Much like the other external reactor. The remainer was far more resistent to dissolving. Some folks and myself suggested is was not pure and had some other gas that could not dissolve. But when we add it to the disc, we can see the bubbles disappear and the internal venturi when it's over loaded after removing the unknow gas bubble and filled with fresh CO2.
Further, the place I get the CO2 is a large scale supplier, they regularly test the gas. Still, I'm not trusting them, I will have the gas analyzed.

This is at 32ppm.

So, the gas coming from the CO2 gas tank should be all the same?
Why would it dissolve so fast then if it's not "pure"?

There might be trace amounts of some "other" gas that does not dissolve well that builds up and as the CO2 is dissolved, the other gas is slowly left over to accumulate.

But how does that explain the internal reactor and external reactor gas bubble that remained after we dumped the unknown gas out and refilled with CO2 from the gas tank raidly?

This other gas mixes with the CO2 and becomes a mist mix.
So I do get lower pH's, but the gas may not be completely all CO2 either.

I also added so much CO2 gas as to drive the venturi after tipping out the unknown gas(Time- PM).

The venturi does indeed produce lots of mist and since the orginal bubble dissolved relatively fast(so we will assume it's not the other unknown gas), the mist did persist and slowly came out of the bottom and slowly rose to the surface.

The mist persisted longer than a few seconds, the same deal occurs with the Disc, pure CO2 comes out and you can watch it completely dissolve early, then persist later in the day.

This tells me that the gas build up may not be exclusively CO2(N2/Ar/O2 all from the gas tank, not from the water itself), but it supports the original hypothese, the mist does indeed persist quite well and is able to do what I suggested prior.

I think what might be occurring is that the other gas is mixing with the CO2 late in the day as the other gas builds up, this mix is spit out as a mist. This mist mixture is able to dissolve the CO2 fraction and leaves the other gas leftover to accumulate.

But, this does not mean the CO2 mist does not persist, your experiment(but using an internal) showed that well with the mist idea when I removed the unknown gas and the venturi kicked on and produced lots of mist.

I suggest you try this with the internal reactors(they are cheap and only cost 2-3$ may 10$ if you make one out Acrylic).

Wait till the end of the day, tip the reactor and allow the gas to escape, next, fill the CO2 reactor up with lots of CO2 gas rapidly till the venturi mist starts coming out and continue and watch the mist.

Then you can be fairly confident of what the gas mist is(at least mostly, since it did all quickly dissolve unlike the build up gas, but....... why does that built up gas dissolve the following morning so fast? That is weird one).

Also, why do the reactors fill up so fast with gas after a water change?
I've inverted them, I know they do not have other gases present prior, I also know from the above control without adding gas, they do not degas the water, I add CO2 and they build up rapidly.

I will be taking my samples to the lab next week as well as gas samples from the CO2 tank to be analyzed in a GC.

We maybe both right and both wrong in part.
CO2 gas does dissolve rapidly, but it persist when misted into the tank.

I'm worried that the gas in the unknown maybe have some CO2, enough to reduce the pH when I tested it by adding the gas to some ambient water and measuring the pH before and after (but not as pure as the gas tank CO2).

Well, I'll find out soon enough how much is what by running the gases through the GC.

Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Try this.

Yep.

If they do not equilibrate, then do they supply the plants with gas CO2?
Hard to find some ways and methods to answer this basic question:

Does the CO2 in the gas mist actually increase growth or not vs a good ambient dissolved CO2 PPM?

The only way I can tell is with measuring the ppm CO2 and then comparing the O2 levels for each.

Whatever the difference is in O2, or dry weight biomass is due largely from the gas mist vs aquaeous. But I don't like that, it's not direct. I want to know what ratio of gas vs aq CO2 the plant is getting.
Labeled CO2 stable isotopes or radioactive C14 will not not work.
I have access to all sort of chemical lab equipment and methods.

This will vary tank to tank and non limiting factors for each must be maintained.
To answer this question, it will not be easy.

I am heading to a lab Tues to sample the gas from the reactor build up as well as the CO2 in the gas tank itself.
I'll use a GC and ask Dave (who's a nut on chemical analysis) to see if we can use some other methods to answer these questions.

I would love to use stable isotopes, C13 or even C14 labeled CO2, but some of gas will still get into the water. I can find out that ratio and then use that to estimate, but it's still not direct.

So some of the dissolved CO2 will get to the plant and some of the gas.
There's no simple way to tease that ratio of gas vs aqueous CO2 apart I know of yet.

That's the main issue.

In the meantime, till we try to get a better handle on it, folks should try the method and give it some thought and observe the growth changes, differences, pearling changes etc.

The how is fairly straight forward, much like adding more nutrients/CO2 =- more plant growth but not algae growth, the why is going to be awhile and I intend to look into it much more than the last month's article did.
That does not answer many things.
I only came up with the idea less than a month or so ago, and have not had much time to test and write the articles etc.

I tend to try something out loking for the more obvious things then if they don't work, keep after it.

Tenacity is key.

So we can go after this question more from here on. But the observation was the starting point..........there will much more about this in the future.

So try blasting the mist, see what you think as far as growth and health for the tank versus the other methods.

I think that is the real issue folks may gain from all of this rather than the why. We can and will work on the Why later.



Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Try this.

How can they become pure O2 or N2(which does not build up diurnally, only CO2 and O2 will) or any other gas more than the air levels present?

O2 is still only at most 30% O2 in that bubble at 150% saturation, and 21% at full saturation.

What's the other gases?
O2 is only 10ppm but the CO2 is 30ppm.

1000% vs 150% is large difference.

The whole issue is tough to ever measure and determine.
I think folks are realizing this more and more.

You can watch the bubbles rise and disappear that are small.

Likewise you can watch them get blown all over the tank late in the day.

If they come out of a disc and persist, what else can be added except from the water?

CO2 is 3x more than O2, so the CO2 bubble deals with lots of excess gas, but why would it dissolve in the beginning from the disc, but not late in the day?

The only two choices are O2 and CO2 then.
And O2 is much less than CO2.
Plant uptake of CO2 is less as the day goes on.

See why I think it's CO2?

I did not think that at first.
I saw intense plant growth and have noticed it where the disc or diffuser mist exits. Tankppm ranges are the same thoughout the tank, but localize growth was always much better.

So I tried adding the mist all over the tank.

Bam, I got the intense growth all over the tank.
We can go on about the how/why, but the usweful issue is that the method is cheap and it works and it's something new to try out as method that will help the plants grow well.

Try it for awhile first, then think about it.
This will not be solved that soon.

I had hoped I could do it in a month, but nope, it'll take a longer time.

Regards,
Tom Barr

















Regards,
Tom Barr

 

Re: Barr Report - Issue 10 - CO2 - Try this.

Pure O2?
The only pure O2 is from the plants, the rest is a mixture of gases.
That's likely why I had the samples depress the pH, there was some CO2 in there also.

Also, there is not a lot of O2 in the water really. 12 ppm is not much.
I have pure O2 that I can add to a tank and have numerous times.

It's some very stubborn stuff to dissolve. There is virtually NO Mist produced when you use O2 gas also.

So based on your observations, is this a good method that deserves some investigation?

Given that folks have a substantial amount of CO2 issues.......

I'm not sure how high you can go with O2.
I ran things at 180% a few times. Algae laughs, perhaps at 200%, then things start to crash due to O2 toxicity.

But who knows in a planted tank.........

You'll note I do tend to push the limits of each nutrient, O2 is a nutrient in a sense.

Also, the rate of degassing also increases as ppm increase in the water. A tank with 500% of CO2 vs 150% will degas faster given the other factors are the same.

As you approach the 100% level, then it tapers off slowly.

I have observed the same thing as you though, many folks now have since I suggested this. The basic question is why.

1. Some increase in the diffusion efficiency/response time can be suggested. This can be measured via CO2 levels.

2.Some increase due to O2 levels(how come the O2 is produced sooner and more of it?) but the growth is different than merely putting non CO2 bubbles all over, we can do that or even use air which has very low CO2, but still some.

So doing the dissolved in solution O2 and CO2 differences leaves the main suspect, the gas phase CO2 isolated. I'm assuming that with the disc mist method, the gas is relatively pure.

We can run the CO2 gas source through a GC and also see about the external reactor gas mixtures as well as the source itself.

Still , how does the gas dissolve from our CO2 sources in reactors/disc, but when added to the tank and through the plants with this MIST idea causes such pearling?

Seems we cannot have both cases occuring simultaneously.
Adhesion of sticky hard to dissolve gas bubbles cannot account for this.
Even if they are hard to dissolve bubbles..............say O2, where did that O2 come from and how could it increase the O2 levels inside the tank if that is the only source of O2?

Some O2 diffusion INTO the bubbles can occur. Much like the diffusion to the air above when it degases.

But is the dissolved CO2 also not doing this same thing and at a much higher concentration than O2 gas? (CO2 is at a much higher ppm than O2)

Still, the bottom line is that folks get more pearling, better growth, less algae.
It might take awhile to figure out what is occuring still.

So Detlef,
Do you think it's better growth or something else?
Do you think something significant is occuring in terms of the plant's growth/health?

Keep doing this method for a few weeks.
I've gotten some awesome growth after large water changes using the same temp water from tanks. The exposure to air allowed the plants to take in lots of CO2.

But this effect is shorted lived(one day maybe two).

The CO2 mist allows this same effect to keep going day after day.

Regards,
Tom Barr