My AGA talk about light and CO2 demand

[Tom Barr]

I focused mostly on CO2 and light relationship, but I hit on a point that was not really discussed...........well.............ever...........

The point is that light and CO2 (and nutrients) are non linear relationships.

In other words, if I add say 0.5 ppm of PO4 to a tank with 5.0 ppm already, it will not affect growth much.
If I add 0.5 ppm of PO4 to a tank with 0.01ppm PO4, it will have a dramatic impact.

Same with light and then some.
If you adjust the light from say 30 umols to say 50 umols, it will have a large impact on growth, but..........it will also have a similar large impact on CO2 demand in plants.
If you adjust the light from say 200 umols to 220 umols, there will be virtually no difference in CO2 demand.

At these lower near limiting levels, we see the most dramatic differences and changes.

 

[spyke]

I never got to talk to you at the convention. But it was very helpful. Especially the part about how all elements work together. The temp, co2, frets, and light. Very insightful indeed. And for all of you who didn't go, sucks to be you. Lol


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[Tom Barr]

I never got to talk to you at the convention. But it was very helpful. Especially the part about how all elements work together. The temp, co2, frets, and light. Very insightful indeed. And for all of you who didn't go, sucks to be you. Lol


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Well, I had 3 talks preferred, but the storm did not prevent other speakers from coming fortunately. I cut the talk down some so I could go over the figures more.
Turned out well.

 

[jerrybforl]

Tom I liked your talk a lot! It made me understand the relationships that much more.

I think only one person gave you grief, and it was the gentleman that said, "I've grown everything for over 40yrs without CO2". Then he went on to say that he had never tried glosso...LOL. I guess not everything.

I think the majority learned and enjoyed your presentation! I'm glad I got a copy of your PP slides. I will definitely use them, hopefully, with a planted club!

In other words, if I add say 0.5 ppm of PO4 to a tank with 5.0 ppm already, it will not affect growth much.
If I add 0.5 ppm of PO4 to a tank with 0.01ppm PO4, it will have a dramatic impact.

Makes complete sense! Same can be said for the other nutes we add to the tank.

Same with light and then some.
If you adjust the light from say 30 umols to say 50 umols, it will have a large impact on growth, but..........it will also have a similar large impact on CO2 demand in plants.
If you adjust the light from say 200 umols to 220 umols, there will be virtually no difference in CO2 demand.

Is there a saturation point as far as absorbing light goes with plants? We spoke that some of your tanks have 400>umol at the substrate. Does this affect your CO2 much as opposed to using 100>umol at the substrate?

Gonna like this thread!

 

[Tom Barr]

I actually like folks to give me a hard time, that's what we do in college grad school...........that way we can answer any question or at least worm and wiggle our way through it.
A good question is worth a lot, that's why I pester some folks like Amano or others that bring things up.
The rest of the cowards do not ask.:gw

 

[jerrybforl]

Same with light and then some.
If you adjust the light from say 30 umols to say 50 umols, it will have a large impact on growth, but..........it will also have a similar large impact on CO2 demand in plants.
If you adjust the light from say 200 umols to 220 umols, there will be virtually no difference in CO2 demand.

Is there a saturation point as far as absorbing light goes with plants? We spoke that some of your tanks have 400>umol at the substrate. Does this affect your CO2 much as opposed to using 100>umol at the substrate?

Was wondering what you thought about this...

 

[fplata]

Same here Tom, I am new to this, but I have an engendering background as well as I am OCD so I tend to read and challenge the norm. I run one of my tanks at near 300 umols to the substrate and based on your writings I have increased the co2 drastically, one of my observations is that if my co2 is too high I reduce the beneficial bacteria (I know this because of ammonia) if I lower it too much I start seeing algae, I can't find that sweet spot. I do run EI on that tank, since the relationship is not linear, I am wondering if I need to drastically increase the dosing?

 

[Tom Barr]

Is there a saturation point as far as absorbing light goes with plants? We spoke that some of your tanks have 400>umol at the substrate. Does this affect your CO2 much as opposed to using 100>umol at the substrate?

Gonna like this thread!

Yes, typically around 200-300 umol, you really see VERY little added growth, it's non linear so the higher you go with light, the less added actual growth you start to see.
If you are at the bare min, then any added light.... makes dramatic differences.

Think about EI dosing, if you dose a little more or less, do you see any difference in growth?
No.

If you dose nothing, and you dose just a small amount, do you see a large effect?
Yes!!

This is why many think there's something magic about dosing lean, they can see the differences in growth with small changes in the ppm's.
They(generally 99% of the time) do not think about light or CO2 in the same way however.

There's strong dependence at the lower or limiting levels, there's no dependence at non limiting levels.
That is the nature of those non linear curves on light, CO2 and nutrients.
Life is not this simple straight relationship as we often like to assume.

 

[Tom Barr]

Same here Tom, I am new to this, but I have an engendering background as well as I am OCD so I tend to read and challenge the norm. I run one of my tanks at near 300 umols to the substrate and based on your writings I have increased the co2 drastically, one of my observations is that if my co2 is too high I reduce the beneficial bacteria (I know this because of ammonia) if I lower it too much I start seeing algae, I can't find that sweet spot. I do run EI on that tank, since the relationship is not linear, I am wondering if I need to drastically increase the dosing?

I think you are gaining nothing except paying a lot more for energy
You are not getting a good efficient return, you are having headaches, and it's unmanageable.

The wise thing to do is cut the light by 1/2 the intensity (see post above). You really are not gaining any more growth or coloration by adding much beyond this. All the CO2/ferts are not going to add more growth and you only invite algae at such high levels if anything goes awry.
High light tanks, very high if you take the older standard, are going to be 90-180 umol at the sediment. Mid maybe 50-90, low 20-50, you can see the widening range as we move upwards in intensity.

While I can easily double my light at the sediment to 300 umol as well, I do not, the plants do better at 150 or so.
No need to add much more than this.

And.....I'll get faster rates of growth because over time, the CO2/ferts are well balanced relatuive to the light.

and that was the point of my talk, to balance all three for a given goal. If you go lean on ferts, then go low on light, lower light will make 99% of the issues go away.
You can still try and use high light, but just be prepared for more failures if you chose that path.

 

[fplata]

Makes since, thanks Tom.

 

[jerrybforl]

Thank you for clarifying this Tom. It makes a whole lot more sense to me now!

It's interesting to know that light, just like other limiting factors, can reach a saturation point.

 

[krandall]

Well, I had 3 talks preferred, but the storm did not prevent other speakers from coming fortunately. I cut the talk down some so I could go over the figures more.
Turned out well.

That way we can use you in another conference soon!

 

[krandall]

I actually like folks to give me a hard time, that's what we do in college grad school...........that way we can answer any question or at least worm and wiggle our way through it.
A good question is worth a lot, that's why I pester some folks like Amano or others that bring things up.
The rest of the cowards do not ask.:gw

Good question, thughtful question, are great. A statement like "I can grow everything." immediately makes my suspect.

 

[Tom Barr]

Good question, thoughtful question, are great. A statement like "I can grow everything." immediately makes my suspect.

He was mostly referring to non CO2 I found out later to support his contention about CO2(acid) consuming HCO3(base). But so if you went with that..........we know there are serious limitations in one's ability to grow everything.
This quickly gets away from chemistry and into horticulture. I think I have grown about 400 species thus far.

In regards to THAT question, we recently had a thread here about the topic so it was fresh in the brain:

http://www.barrreport.com/showthread.php/11066-Different-CO2-forms-under-low-vs-high-pH/page3


The last post summarizes.

 

[Tom Barr]

That way we can use you in another conference soon!

Feel free to use and abuse as the AGA sees fit.
I try to answer questions, then pose others for the next step.

 

[Wet]

*If* you ever want your slides or other material hosted on rota.la, please let me know. It is built such that anyone can take it over (or help host!) anytime it is ever needed.

 

[Texex94]

That was one of the few talks I have the chance to sit through and it was an EXCELLENT talk. I really enjoyed and learned something new. I'm just sorry you didn't get more than one opportunity to speak at the convention. I think we all would benefit from your experience!

I found the "chemist" who argued about buffering to be out of line and am glad someone pushed on so others could ask questions.

Looking forward to your next talk!

 

[krandall]

I don't think we'll let it be so long before we get Tom back again!

Maybe we'll have to use Erik's "claw" (usually used for placing AV lights) for removing hecklers from the room! I think that even if someone strongly disagrees with a speaker, and even if the person is right are right (not that this guy was) it is terribly disrespectful to start arguing with a guest speaker in front of an audience.

 

[Tom Barr]

*If* you ever want your slides or other material hosted on rota.la, please let me know. It is built such that anyone can take it over (or help host!) anytime it is ever needed.

Thanks Wet, nice meeting you also! Good to put a face to the on line persona.
Yes, we can do that or folks can simply get the AGA's DVD. Good stuff and if you cannot stand me for more than 10 minute blocks, not bad either

I think I'll likely compress into a pdf file and post here for the "subscribers" and not the "members".

 

[Tom Barr]

I don't think we'll let it be so long before we get Tom back again!

Maybe we'll have to use Erik's "claw" (usually used for placing AV lights) for removing hecklers from the room! I think that even if someone strongly disagrees with a speaker, and even if the person is right are right (not that this guy was) it is terribly disrespectful to start arguing with a guest speaker in front of an audience.

I've disagreed with folks in the past, but if you are nice and ask them later after the folks and crowds have moved on, that is okay.
My points tend to be questions. Not corrections, that's the audience and other folk's job.

Someone got me stretching the truth, hyperbole etc on TPT recently, I'd been saying my 180 was 7-8 years old, but it's only been up since 2007 later and 2008 early operational. My bad.
We should never blindly follow anyone, I might be wrong. I try not to be, but even Paul Sears was incorrect about PO4 and algae, that guy is super smart, has a Ph.D. etc.
But like anyone wise enough, if you are fairly sure you are wrong, admit it and move on. Don't repeat the mistake over and over.

Such fear and arguments often drive people's ego to research and make sure they are correct and look into the issue more, we should NOT be smug and so sure of ourselves.
Something are okay, eg, the earth is not flat etc. Falsification etc. Those we can be pretty sure about.

This process tends to work for me, others may view it as argumentative at the personal level.
In the context of a meeting, it's not really wise, but I've heard folks go after Heiko on a number of things.
Sometimes the error is a bit too much for some to handle, but that was the group, not just one person in the crowd.

Some folks may also view the debate as academic bore. I view it as a good opportunity to hash out somethings with someone else who actually cares about it enough to talk.
In some ways, you are "selling" a type of logic or common sense. Does a reasonable person buy what you are saying or agree with it based on your talk and what they think they know to be true, or likely true?
That's generally what I ask myself and how view other folk's talks