# Questions about Tom Barr's Algae findings.



## Jarrod987 (Aug 18, 2015)

I used to be a big fan of the control PO4 and NO3 to control Algae. I admit, I still kind of like it in fish only tanks. However, I am doing a lot of reading on Tom's findings with planted tanks and I think it is fascinating stuff. I would first like to make sure I am understanding what he is saying, then ask a what if scenario or 2 that I don't know what would happen.

First, it seems like he is saying that PO4 is not directly limiting Algae, it is just indirectly limiting it by decreasing the plants need for CO2. Says you could do the same thing with light etc. Is this correct?

Second, It looks like he is saying when you only limit one factor that CO2 seems to be the real trigger for Algae. That it is low CO2 that triggers it? That what nutrients are present have a role in which type you get?

Is all that correct?


So If a person had an algae outbreak in there planted tank they could bump up CO2 and get rid of algae? Is that what he means?

I wonder if it is the presence of CO2 that is toxic to the Algae? That would be fascinating because H2O2 seems to kill algae very fast too.

Or is he saying that higher CO2 just lets the plant beat the Algae?
If nutrients and light are non limiting then it cannot be that the plant just out competes the Algae for nutrients right?
Is he saying the plant just starves the Algae for CO2? Or is it Alelopathy? Does he know why higher CO2 prevents algae?


Now what about in a fish only system with no plants at all.
Suppose there was an algae bloom, non limiting nutrients, same light intensity etc...
Could adding CO2 get rid of the algae? That would remove the out compete and alelopathy theories. It would have to be that the presence of enough CO2 somehow interfered with the Algae?


I think this is a fascinating discovery. I would really like to understand this model better. I want to play with this one in my test tank


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## JeffyFunk (Apr 6, 2006)

no. i would summarize tom barr's work as being (1) CO2 is harder to control than you think and (2) focus on the growing conditions needed to grow the plants and thus algae will be limited. you're interpreting nutrients as algae control and that's not really how you should interpret tom's work.



Jarrod987 said:


> First, it seems like he is saying that PO4 is not directly limiting Algae, it is just indirectly limiting it by decreasing the plants need for CO2. Says you could do the same thing with light etc. Is this correct?


kinda... a long time ago, it was thought that excess phosphates caused algae. tom barr helped to prove that this was not the case. diana walstad also found this out by finding research papers that state that algae only needs as much as 0.01 ppm phosphate to continue to grow. hence, the idea that algae growth can be limited by limiting phosphates is not true.

so yes, phosphates are not directly limiting algae.

i don't believe you are correct in stating that phosphates indirectly limit it by decreasing the plants need for CO2. what i believe tom barr has said, though, is that some plants are often times better able to deal w/ limiting phosphates than limiting CO2.

what are you saying about light? you are correct in that decreasing the amount of light will decrease the overall demand for nutrients, CO2 included, however.



Jarrod987 said:


> Second, It looks like he is saying when you only limit one factor that CO2 seems to be the real trigger for Algae. That it is low CO2 that triggers it? That what nutrients are present have a role in which type you get?
> 
> Is all that correct?


tom barr believes that every problem is related to CO2. war is caused by inadequate CO2. hair balding is caused by inadequate CO2. i agree with him that CO2 is often times a difficult thing to get right. i agree w/ him that growing better plants is often times a result of needed non-limiting CO2. but i'm not sure low CO2 triggers algae, though. maybe indirectly by causing stress to the plants, but that's it.

i do believe the algae type you get is directly related to the presence or absence of specific nutrients. it's a very good way to help determine what nutrients you are lacking (or in excess of). i would say that actually testing your water is the best way, though, of determining the nutrient content of your water and your plants demand.



Jarrod987 said:


> So If a person had an algae outbreak in there planted tank they could bump up CO2 and get rid of algae? Is that what he means?


See previous response...



Jarrod987 said:


> Or is he saying that higher CO2 just lets the plant beat the Algae?


YES! THIS!



Jarrod987 said:


> If nutrients and light are non limiting then it cannot be that the plant just out competes the Algae for nutrients right?


YES! THIS! however, i will add the caveat that having ALL your nutrients, including CO2, be non limiting is more difficult than it sounds...



Jarrod987 said:


> Is he saying the plant just starves the Algae for CO2? Or is it Alelopathy? Does he know why higher CO2 prevents algae?


no, he's stating that if plants truly have all the nutrients and light that they need so that nothing is limiting, then they will grow just fine w/ no algae. the issue, of course, is making sure all the nutrients are non limiting.



Jarrod987 said:


> Now what about in a fish only system with no plants at all.
> Suppose there was an algae bloom, non limiting nutrients, same light intensity etc...
> Could adding CO2 get rid of the algae? That would remove the out compete and alelopathy theories. It would have to be that the presence of enough CO2 somehow interfered with the Algae?
> 
> I think this is a fascinating discovery. I would really like to understand this model better. I want to play with this one in my test tank


if you have a fish only tank, you would lower the light intensity... done. why would you waste the money on expensive lighting and a co2 system if you don't have plants?


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## BruceF (Aug 5, 2011)

Well done Jeffy.


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## Jarrod987 (Aug 18, 2015)

Sorry if I wasn't clear about the nutrient/Phosphate issue. I read where Tom was talking about how limiting phosphate was really just causing the plant to use less co2 which I guess causes a buildup of more co2 in the tank which then caused the algae to switch off.

I was trying to say that PO4 is not actually the trigger of algae like I thought It was 
He also said you could do the same trick with light but that it was not the trigger either.

So Tom believes CO2 is the secret and not everyone agree's it sounds like  It also sounds like maybe he doesn't know exactly why it would work.

I think to some up he is saying that if you make an optimal environment for Algae, you will get algae (various types for various conditions), if you make an optimal environment for plants, you will get plants and probably no algae. The algae seem to know it is not there time to germinate as he says.

Is that about right?
I think I have come to a new view that is more holistic, Light, CO2, Nutrients..all play a role and when you get different combinations you get different algae or, if you get it right, plants and no algae 

Far as fish only tanks goes, I like bright tanks  I have good luck with PO4,N03 removal methods and so I will stick to that for those tanks If I need to. I really like knowing how it all works though. I already have a nice Walstad tank that is 2 months old. I think I may try one of Tom's EI tanks now.

Something I have heard people disagree on and wonder about. I know that too many Micro ferts can be toxic. I was wondering if not enough can be just as limiting as N,K,or P? There is no way to test them  Well...Maybe an iron test as an index?

Thanks folks.


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## JustLikeAPill (Oct 9, 2006)

Sounds like you are talking about Liebig's law of the minimum. I remember that from my sophomore ecology class. Growth is controlled by the limiting factor. Not enough of any of them will retard the growth and uptake of others. Micro-nutrients re only needed in small amounts, so something like a boron deficiency is unlikely to occur if you are dosing a good micro blend.

I think this is what you are referring to: 
https://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum


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## Jarrod987 (Aug 18, 2015)

JustLikeAPill said:


> Sounds like you are talking about Liebig's law of the minimum. I remember that from my sophomore ecology class. Growth is controlled by the limiting factor. Not enough of any of them will retard the growth and uptake of others. Micro-nutrients re only needed in small amounts, so something like a boron deficiency is unlikely to occur if you are dosing a good micro blend.
> 
> I think this is what you are referring to:
> https://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum


Yes I'm talking about Liebig's Law of the Minimum. I was just wondering if it applied to every nutrient. Even the micro ones. I don't expect to have a shortage. I am just wondering if there was one, would it have the same effect.


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## niko (Jan 28, 2004)

Also please note that:

- Not a single tank in the ADA yearly contest is run according to what Barr says. 
- All US planted tank forums (not just APC) barely present any aquascapes and the emphasis is on equipment, chemicals, and issues.

Choose what your hobby will be. Both choices are full of smoke and mirrors. And both can be fulfilling.


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## houseofcards (Feb 16, 2005)

Good co2 is certainly a part of the equation, but so is light, ferts, feeding, lifestyle (yes lifestyle), etc. 

Co2 will help more in a densely planted setup, but why would it help in a thinly planted one. Co2 in itself is not an algaecide. It creates superior growth which in term increases uptake and crowds out algae. That's why the most challenging setups in terms of algae control are high-light, high stock, low plant mass. 

There are so many factors that go into an algae free tank that you really can't put your finger on one specific factor. You need to simply be disciplined in what you put in, and how you maintain it.


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## Jarrod987 (Aug 18, 2015)

houseofcards said:


> Good co2 is certainly a part of the equation, but so is light, ferts, feeding, lifestyle (yes lifestyle), etc.
> 
> Co2 will help more in a densely planted setup, but why would it help in a thinly planted one. Co2 in itself is not an algaecide. It creates superior growth which in term increases uptake and crowds out algae. That's why the most challenging setups in terms of algae control are high-light, high stock, low plant mass.
> 
> There are so many factors that go into an algae free tank that you really can't put your finger on one specific factor. You need to simply be disciplined in what you put in, and how you maintain it.


I have about 18 plants in a 20 gal. Most are doing ok but no growth. one of the woody stemmed ones is loosing leaves even though I have 1 ppm phosphate. It has big holes in the leaves that remain which make me suspect lack of carbon. I have high alkalinity (8DKH) I also add excel. Maybe not enough? No way to measure it. When I calculate my available co2 it comes out to 2.5ppm pretty low even if my guess is way off?


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## f1ea (Jul 7, 2009)

Is this tank a typical soil Natural tank?

You're posting in the Natural subforum but asking about Excel, dosing and EI...... so not sure what method your tank set up to be in terms of substrate, lights, plants, dosing, etc.

If you have slow growers and low light, slow growth is absolutely normal.

Are you confusing yourself? 

Pick 1 method. Start simple and take it from there. Usually, starting simple means low-ish light and easy plants 

BTW all the responses above are awesome.


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## Michael (Jul 20, 2010)

Truthfully, a discussion of EI and artificial CO2 supplementation is out of place in this forum. I am going to move the thread to "Fertilizing". I have no problem at all with the thread or any of the individual posts.


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## JustLikeAPill (Oct 9, 2006)

Jarrod987 said:


> Yes I'm talking about Liebig's Law of the Minimum. I was just wondering if it applied to every nutrient. Even the micro ones. I don't expect to have a shortage. I am just wondering if there was one, would it have the same effect.


Oh yes, absolutely applies to every nutrient! Same effect.


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## f1ea (Jul 7, 2009)

Michael said:


> Truthfully, a discussion of EI and artificial CO2 supplementation is out of place in this forum. I am going to move the thread to "Fertilizing". I have no problem at all with the thread or any of the individual posts.


Yeah. The discussion is nice. Pretty good actually.

But it's a bit confusing to get an idea what sort of tank/light/soil/plants etc the OP was talking about when mentioning some of his problems and questions. In fact, i still don't know hehehe


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