# why use co2?



## amano101 (Dec 21, 2008)

Why is it that when we have algae issues, were supposed to bump up the co2? What's the science behind it? I always assumed the change in ph was ok for plants but not algae, but that just doesn't sound right to me. I have a few other ideas floating in my head but I'm just not sure. Anyone know?


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## amp (Dec 2, 2008)

More CO2 = plants grow faster, then the plants out compete the algae keeping it in check. I dont think it has anything to do with the pH change.


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## plantbrain (Dec 15, 2003)

Poor CO2+ high light = no plant growth.
Algae grows when the plants do not do well.

The goal here is to grow plants, not kill algae.
Careful not to put the cart before the horse.

This may not always be the case, but folks tend to get a lot more light than they bargined for.

Algae are never CO2 limited, plants are very very often are.
CO2 is very tough to measure and changes rapidly, nutrients and light, not very much compared to CO2.

Folks also do not measure light, so it's hard to tell how much light is being added. Lessis better because light drives CO2, less light = less CO2 demand from plants.

That makes it easier to target a good manageable CO2 rate.

This also explains why some folk have good results with less, and others have more troubles. Many think more is better with light, so they get that first, then struggle, add CO2 later, don't adjust it right, have more troubles at high light etc.

If the goal is to grow plants well and healthy, then add plenty of CO2 so that it is non limiting. Then nutrients and moderate to low light.

That will reduce algae getting a foothold.

Regards, 
Tom Barr


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## manofmanyfish (Mar 31, 2008)

plantbrain said:


> The goal here is to grow plants, not kill algae.
> Careful not to put the cart before the horse.
> 
> Regards,
> Tom Barr


Growing plants (if that's your goal), and getting the light/CO2 right is much more difficult than it would be if your goal was simply having an aquarium with fish as your primary objective and having plants secondary.

IME, the plant objective is far more difficult or a much bigger challenge than simply having a nice aquarium with wonder fish. In other words, fast growing plants under water ain't easy. It might even be over rated.


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## macclellan (Dec 22, 2006)

manofmanyfish said:


> IME, the plant objective is far more difficult or a much bigger challenge than simply having a nice aquarium with wonder fish. In other words, fast growing plants under water ain't easy. It might even be over rated.


Huh? There are lots and lots of plants that are very easy to grow underwater, and fish-only tanks don't fare well compared to planted tanks in terms of beauty with a few exceptions. If you think they are overrated... wrong forum maybe?


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## manofmanyfish (Mar 31, 2008)

macclellan said:


> Huh? There are lots and lots of plants that are very easy to grow underwater, and fish-only tanks don't fare well compared to planted tanks in terms of beauty with a few exceptions. If you think they are overrated... wrong forum maybe?


Oh, I agree. I have absolutely no problem growing a tank full of beautiful plants...and it is easy...very easy....What I can't do, it do it without having constant algae battles. I grow the plants so fast that the tank becomes nothing but crammed full of densely packed plants. I'm not very good at getting it to "stay" at the right amount of plants. I have a cycle of lots of growth which equals lots of change, pruning, cleaning and the look changes. I thin it back to the right balance and do it all over again.

I have a low light tank that has equally beautiful plants but is much more stable in every way. It isn't constantly going through the cycles.

Just out of curiosity, if I decide to go with "plastic" plants, the plantedtank forum would frown on that?


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## Hoppy (Dec 24, 2005)

manofmanyfish said:


> Just out of curiosity, if I decide to go with "plastic" plants, the plantedtank forum would frown on that?


Of course not, if you promise to find a way to breed those plants.


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## NightSky (Feb 16, 2009)

manofmanyfish said:


> Just out of curiosity, if I decide to go with "plastic" plants, the plantedtank forum would frown on that?


That's like asking a fish forum if it's ok to have plastic fish. You can do it, but it isn't much fun or as aesthetically pleasing.


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## amano101 (Dec 21, 2008)

thanks guys, that was one of the ideas floating around in my head and now I know why bumping up co2/ferts isn't a cure all.

edit- on a second thought, im still a little confused. so the theory is "algae use the extra light not used by the plants to grow." if there is not enough co2, then the plants will use less light and reflect what is not used. this would create more energy for the algae to grow off. 

the other way i can take this is- algae do not only rely on light, but also the nutrients in the water. if the correct balance of co2, lights, and ferts is not used then algae will be able to use the excess stuff not being used by the plants. this one would make more sense. if this is true then i finaly understand why a natural "low tech" planted tank is so much easier. on another note i will be trying both an extremely low tech tank and a fairly high tech tank as my first planted tanks, so it should be interesting seeing the difference first hand. 

its super late right now. sometimes i ask stupid questions that i fully understand when im not so tired. thanks for all the help and understanding.


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## Homer_Simpson (May 10, 2007)

amano101 said:


> ...edit- on a second thought, im still a little confused. so the theory is "algae use the extra light not used by the plants to grow." if there is not enough co2, then the plants will use less light and reflect what is not used. this would create more energy for the algae to grow off.
> 
> the other way i can take this is- algae do not only rely on light, but also the nutrients in the water. if the correct balance of co2, lights, and ferts is not used then algae will be able to use the excess stuff not being used by the plants. this one would make more sense. if this is true then i finaly understand why a natural "low tech" planted tank is so much easier. on another note i will be trying both an extremely low tech tank and a fairly high tech tank as my first planted tanks, so it should be interesting seeing the difference first hand.
> 
> its super late right now. sometimes i ask stupid questions that i fully understand when im not so tired. thanks for all the help and understanding.


Well, the way that I understand and someone correct me if I am wrong it is that the lighting intensity is really the critical piece here. Therefore, C02 is not really a necessity unless you are starting a planted tank with really high(3+ watts per gallon) light intensity. Often times, just reducing light intensity, at least in my experience, is sufficient to ward of algae or keep it from overtaking a tank. Light intensity as I understand it drives the plants needs for everything: c02, nutrients, etc., So, if you start with the premise that more light means better plant growth and go ape on light levels, then the ultimate opportunist: algae will rear it ugly head and capitalize on the fact that the plants will not be able to grow well at those extremely high light levels as they are lacking sufficient c02 and nutrients to keep up with the light levels. When the light levels are reduced, the plants will grow slower but not necessarily unhealthy and their demands for c02 and nutrients will be much less giving you more wiggle room(to use Tom Barr's words) to more easily target sufficient c02(which may not even be necessary and Seachem Excel may work as well) and nutrients. 

When you see algae outbreaks in nature that are often blamed on run off of nitrates and phosphates from farm feritlizer, this is not normally happening in densely planted lakes and rivers, so of course algae will feed off high nitrates and phosphates in the absence of plants. The same reason that we sometimes see algae in unplanted, poorly maintained and overstocked unplanted tanks.


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## amano101 (Dec 21, 2008)

what nutrients do fish give? people always talk about their tap water not having enough of a certain fert so they bump up that fert to even it out and it seems like what the fish give isn't considered. if a plant doesn't have enough of a certain chemical to complete photosynthesis, how much would that affect light and co2 used?


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## amano101 (Dec 21, 2008)

since its close to the topic- i'm not too sure on ei, Tom. i know you put a lot of work into the method and i haven't read most of the your reasoning behind it. it seems to me like everyones tanks are going to be drastically different and fert dosing has to be individual to the tank in order to grow plants well, without algae outbreaks. it even seems like after testing for ferts in the water, dosing will still be ei, since it would still be off from what the plants actually use. i will read everything i can that you wrote, later. i just got off work and i'm feeling lazy right now. is there a short answer to this or should i just read and figure it out and talk to you later?


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## Hoppy (Dec 24, 2005)

Algae, once they start growing, require very little to keep on growing. But, they don't start growing unless the conditions are such that their genetic make up tells them they can complete a life cycle and reproduce. So, if we prevent those conditions from ever happening, algae should just remain as dormant spores. One of those conditions seems to be ammonia in the water. Another seems to be big changes in CO2 concentration in the water. That way of looking at it fits our observed facts better than anything else I have heard or read.


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## plantbrain (Dec 15, 2003)

manofmanyfish said:


> I have a low light tank that has equally beautiful plants but is much more stable in every way. It isn't constantly going through the cycles.
> 
> Just out of curiosity, if I decide to go with "plastic" plants, the plantedtank forum would frown on that?


Wise in the first statement and No to frowning to the second onplastic plants, but only if..............you have matching plastic fish to match the plastic plants.

Real fish are so hard to keep, they die easy, you have to feed them, you have to heat the tank and buy a heater, you have to change the water.........

:redface:


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## plantbrain (Dec 15, 2003)

amano101 said:


> since its close to the topic- i'm not too sure on ei, Tom. i know you put a lot of work into the method and i haven't read most of the your reasoning behind it.


I do more than *one* method:thumbsup:



> it seems to me like everyones tanks are going to be drastically different and fert dosing has to be individual to the tank in order to grow plants well, without algae outbreaks.


Don't fall for this they are too individualistic balony. That's politcal mumbo speak. You can figure this out and understand the larger picture here.
Then you can see that the methods are not that different and that algae is not limited, outcompeted etc.

People treat their tanks differently, but they fail, not the methods:redface:
All methods "work", but at different rates.

A non CO2 tank achieves no water changes, no dosing(fish waste and sediment perhaps does that role), easy to care for. What's the trade off? Cannot keep some species, and the rate of growth is 10-30X slower than that of a high light CO2 tank.

Light energy is very low.

A low light CO2 enriched tank, the rates are 5X more than the same light vs the non CO2, and you can grow more species. 

Growth rate is higher, the required work is more/input is higher(CO2/more nutrients)

Med light etc.......

And high light with good nutrient dosing/CO2(both high)........grows plants the fastest.

Most folks want good growth, but manageable, so the low light CO2 enriched option is best. Some think that more light is better, only to find out they have trouble managing it. However, when it comes to algae isues, all these tanks get algae for pretty much the same reasons: poor care of the plant demands for that rate.

Algae live in natural systems and are seasonal, thus their resting spores(think algae "seeds") sit and wait for a large run off from the land into the stream, or lake, spring melt, clear water, high light before the forest canopy closes in for summer etc.

If you stop germination fo algae spores.............then you stop algae.
Same with weeds, if you destroy the propagules, then you stop algae at the root.

Very poor algaunderstanding promotes a great deal of myths in this hobby and I've never seen a method yet that addresses algae. EI really does not, it ignores the claims about excess = algae. It focuses only on plant growth. No other method suggest excess nutrients do not cause algae, yet we can test and prove this to be so time and time again.

So why do folks keep saying these myths?
See the above, the method does not fail, we do.
We like to blame the method rather than ourselves, some folks are successful with any particular method and some fail. This is true for all methods.

The human factor cannot be ignored.

Also, many do not take kindly to being told they ae wrong about excess nutrients not = algae bloom.

Their ego's are at stake. Many have poo pooed me for this. I really don't care, they will have to deal with their fragile ego syndrome. I'm more interested in the issue and topic. Not making sure they do not get their feelings hurt when they stray off topic. Folks need to take things witha grain of salt on the web as it is.



> it even seems like after testing for ferts in the water, dosing will still be ei, since it would still be off from what the plants actually use.


Yes, you and I can both make this point and agree, some will claim they(and/or you) must test anyway.



> i will read everything i can that you wrote, later. i just got off work and i'm feeling lazy right now. is there a short answer to this or should i just read and figure it out and talk to you later?


Yep, pretty much
Ya got lots of reading to do if you read everything I write:redface:

I do not ask for faith, I ask for the person to prove things to themselves.
I think about folks here and elsewhere more like students that are curious.
Some are not, they really do not care of some aspects. Some just want a nice tank, and do not care much about the rest.

Sadly, this latter group is not truly fascinated with nature, because if you are.......you wan to know why nature works, how, and you are passionate about that. You do not get to say you do not care only when it suits your argument:icon_roll

That's not fine.

It's also like owning a dog, but learning little about how to train and care for them correctly. There are no bad dogs, only bad dog owners, same deal here, there are no bad planted tanks, only bad neglectful owners.

You are not going to immediately train the dog to do tricks and behave correctly, nor are you going to learn everything about planted tanks right away either.

Patience. 
Same for a guitar playing, Mt Biking, technical skills and knowedge takes time to acquire. Be kind to yourself about it. You get what you put into it.

FYI,
I was intimidated about KNO3, PMDD, chemistry, latin names of plants, CO2, gardening scaping etc etc...........we all started out knowing nothing. PhD, or the 2nd grade..............I haggled with PhD's, still do, have to tomorrow in fact on Weed Science with some of the top folks, but they are people, and they also did not always have PhD's, they came from the same place I did.
Like all of us.

While some in the hobby are into it more than others..........some simply do not have the time or that much interest, they have othe passions, work, kids, wife, hubby, like playing bass or MtBiking whatever..............

It's just not worth it to them.
That's cool too, whatever level you want to put into it is fine.

Most are just glad you are into this hobby.:thumbsup:

As you learn more, it starts becoming easier.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

Hoppy said:


> Algae, once they start growing, require very little to keep on growing. But, they don't start growing unless the conditions are such that their genetic make up tells them they can complete a life cycle and reproduce. So, if we prevent those conditions from ever happening, algae should just remain as dormant spores. One of those conditions seems to be ammonia in the water. Another seems to be big changes in CO2 concentration in the water. That way of looking at it fits our observed facts better than anything else I have heard or read.


Well, we can add light intensity/duration as well.

Algae did not evolve in planted tanks, it evolved elsewhere in natural systems that have seasonal cycles, same for the plants.

Water levels also change, ice forms, runoff during spring melt, rainy seasons etc........then a lot of organic matter runoff comes into the streams and lakes, ponds, turnover etc, pulling up all is material and causing the O2 levels to drop, the light to change, warmer temps, CO2 levels go way up, then the water clears, the CO2 drops.........plenty of N around...........seems like a good time to grow, partiularly before the canopy and aquatic plants start shading the stream, lake edge etc.

Just think of the dramatic changes a wetland goes through each year in its natural state. Why are aquatic weeds so bad? We provide a stable water level for them to grow year round. But we need flood control and water supply.

So we try and manage the weeds.

We sort of do the same thing here with plants, we grow them lke crops.
Algae are a bit like weeds.

If the crop is grown well(say a pine forest for paper milling/lumber), then the weeds are less of an issue. The pine forest blocks the light, sheds needles and modifies the system. Same for the aquatic plants. They define the system if their needs are met well.



Regards, 
Tom Barr


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## manhatton (Oct 17, 2008)

Leave it to Tom to drop one of these ^^^^ every once in a while. Although I'll never get comfortable with the term "poo pooed", everything else was gold in that post. 




Hoppy said:


> Of course not, if you promise to find a way to breed those plants.


Ha ha ha! Awesome.


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## manofmanyfish (Mar 31, 2008)

So wait a minute, even if I have plastic plants and plastic fish, I'll still have algae....well that won't be so bad as long as it's plastic algae?


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## EdTheEdge (Jan 25, 2007)

Why use CO2? For many reasons. Most of them *green*.....


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## amano101 (Dec 21, 2008)

i like the way you think, Tom. you might be getting a few more questions/arguements out of me after i read more of your stuff. out of curiosity, who are the weed science people you talk with? is this part of your job? i've been trying to figure out a career i want to pursue for the past few years. i know i want do do something with the environment, and i dont want to have to worry about money all the time. im just looking to see if you have any ideas that fit the description. if so, i'd appreciate a pm. 

Thanks,
Mike


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