A Different Co2 Theory

[akudewan]

I'm a member of a local aquarist group, and some guys were having a discussion on an alternate theory about CO2. While most of us pump CO2 into the water, and try to increase the concentration of CO2 in the water, these guys did an experiment. They made a large amount of surface agitation, using powerheads and spraybars. They noticed that the plants show the same amount of growth, without adding any CO2.

The principle is that there is 0.3% of CO2 in the atmosphere, while in the water, the CO2 is used up by plants, and drops to a level much lower. By creating huge amounts of surface agitation, the CO2 in the atmosphere dissolves in the water. Thus, the plants get a constant supply of CO2, and even though the quantity is small, they get the CO2 constantly.

They argue that this is how the plants in rivers and streams grow well, just because the supply of CO2 is constant, though small.

What are your opinions on this ?

 

[Incitic]

Sounds interesting.

With all the surface agitation wouldnt a strong current emerge?

 

[jimbooo]

i understand the theory but dont believe it will work

co2 is not very soluble, even if the agitation did dissolve an ammount of co2 it would instantly vanish again due to the agitation.

you may increace it from say 2ppm to 5ppm but your never going to get 30ppm that way.

if anyone more awake than me would like to reword that in scientific fashion feel free.

 

[George Farmer]

I was of the understanding that plants need around a minimum of 15ppm CO2 to acheive any noticeable extra growth. This level would be impossible to acheive using surface agitation.

Plants find it quite hard to assimulate lower CO2 levels and this is why an "overpressure" of say 30ppm is often used.

Interesting theory though, I just find it hard to believe it can work as effectively as standard injection.

I also thought the waters in nature were CO2 rich due to decomposing matter etc, this applies to lakes more than flowing waters obviously where the CO2 is driven off. I'm not sure if CO2 levels are actually much higher in fast flowing streams etc.

What does zig think?

 

[zig]

I was of the understanding that plants need around a minimum of 15ppm CO2 to acheive any noticeable extra growth. This level would be impossible to acheive using surface agitation.

Plants find it quite hard to assimulate lower CO2 levels and this is why an "overpressure" of say 30ppm is often used.

Interesting theory though, I just find it hard to believe it can work as effectively as standard injection.

I also thought the waters in nature were CO2 rich due to decomposing matter etc, this applies to lakes more than flowing waters obviously where the CO2 is driven off. I'm not sure if CO2 levels are actually much higher in fast flowing streams etc.

What does zig think?

What i think is that i wont be trying it any time soon on a tank with 3WPG

Naw but seriously i have never heard of this theory, but i would imagine Jimboo is correct, even if it did work how long would the co2 be available for, i would say it would nearly instantly evaporate due to the surface turbulance, but interesting i heard it here first anyway if something does come of it and it gains popularity.

I wonder how long they carried out the experiment for, days, weeks, months? and how much light did they use?

 

[jimbooo]

yeah i'd be interested to hear more details aku. as per zig's questions.

 

[akudewan]

The guy who tried this out (and still does it) has 160W over a 55g. The lighting is moderate, there were minor algae problems in the beginning, but nothing now.

He says the plants are growing well...but he never compared the results by actually adding CO2...

I'm currently trying it out on my tank. I'll keep you posted. This IS interesting

 

[rdd1952]

I am still learning all the nuances of plants and their needs. One thing I learned pretty early on was that in order to increase oxygen levels, you create surface disturbances. It seems that their excess surface agitation would do exactly the opposite and drive almost all of the CO2 out of the water. Just my opinion though.

 

[Lateral Line]

>>> He says the plants are growing well...but he never compared the results by actually adding CO2...

Of course, there are a lot of plants that will grow perfectly well in a tank like that without any CO2 fertiisation at all, so without knowing more details, the fact that his plants are doing well proves nothing. Also, if he has never compared the result of his set-up with a traditional set-up, then again, he is not making a very strong case.

I agree with the others, you may be able to raise the CO2 level by a couple of ppm, but you'll never get it up high with that arrangement.

 

[akudewan]

I've noted one difference of opinion. The people of the local group think that by creating surface agitation, the CO2 levels will "equalise" with the atmosphere, whereas the guys here mostly think that all the CO2 will be "driven out."

There's another guy a-s-k group who has tried it out. He's one of the mods, here is his opinion:

Look at it this way.. vigorous aeration or agitation is akin to
the natural habitat of many plants. Imagine a waterfall, rivers etc..
The gas exchange will make the water equalise with air.. that's the
max. level naturally. I can safely (See 1) say that all aquatic plants
in nature can get only this much of O2/CO2 from AIR and of course
don't forget that these water bodies probably have low nutrients
(no PMDD) the fish supply the whole deal..

As long as the bioload (plants etc.) is similar to nature i.e.
as densely planted as in nature then the above method should meet
all the requirements.. hypothetical.. take a good look at some local
rivers in Kerala (closer to source than sea) and ponder.

I have a tank like this with dense growth. Out of all my tanks
I have only one with CO2 !

CO2 + (PMDD or (MicroNutrients + fish load)) + good lights
results in rapid and ego satisfying growth. While the PMPT (poor
mans planted tank) will grow slowly and easier to manage and
understand.

It all depends which route you want to take. Why not
emulate nature the whole way, its a great working model !

Comments on the natural model Nim or anyone?

Cheers

BTW Kerala is a beautiful place in India, one of the tourist hotspots

Ultimately, it does seem that adding CO2 without any surface agitation is the best way for plant growth.

But I'm still interested in trying out the surface agitation path. My tank temperature is rather warm, and if the agitation doesn't help the plants, then the oxygen will definitely help my fish

More opinions are welcome.

Edit: here is a link to the a-s-k (Aquarists of India) group if anyone is interesed. I hope the mods don't mind: http/groups.yahoo.com/group/A-s-k/

 

[jimbooo]

hmm still dubious but i see his point. what the hell give it a try aku and let us know how you get on. i dont think i'll be following though.

 

[iggy01]

I see no reason why this method wouldn't work as long as the lighting is kept to 2 WPG or below. 3 WPG is too high IMO and would only lead to problems.

However, I don't think the growth rate would be anything like a CO2 injected tank.....probably about 10 x slower. The CO2 would probably reach equilibrium at about 2-4 mg/l.

How often do they do water changes? A similar method to this has been around for a long time, but water changes are usually only done when plants are rearranged, uprooted etc....every 3-4 months or so.

You don't need to restrict surface agitation in a non-CO2 tank IMO.

Interesting topic anyway!

 

[kenneth_kpe]

interesting..... this might be usefull for smaller tanks which are for most of the time exposed with lower lighting due to its small size.... cant the co2 levels be measured accurately ? does anybody have a really sensitive ph meter ??

 

[jimbooo]

Hi Aku,

so any more news on this theory? did you try it or have any feedback from your aquarists group.

just wondering what happened..

James

 

[akudewan]

Hi Aku,

so any more news on this theory? did you try it or have any feedback from your aquarists group.

just wondering what happened..

James

I tried this out myself for sometime, but my plant growth started reducing, so I went back to the good ol' CO2 method.

Many guys have tried this (guy called Nimish in London has also tried it). Plant growth is better than a non CO2 tank, but not as good as a CO2 tank. Doesn't work for high-light setups, as it is known to cause algae albeit in small amounts