# Co2 in a low tech



## Alastair (1 Jan 2013)

I've run high tech tanks before and just about to being to an end my low tech puddle, but was just reading on another site and came across this 

"The second is increasing turbulence. There are arguments for and against this, but for tanks without CO2, turbulence should increase both oxygen (O2) and CO2 for your plants. Turbulence works by allowing better gas exchange between the air and the water and, as concentrations of CO2 are generally higher in the air than in the water, creating turbulence or adding an airstone will increase the dissolved concentration of CO2. This will also increase dissolved O2, which livestock, bacteria, and plants also require to thrive. It will also prevent CO2 and O2 levels from undergoing excessive fluctuations within the tank due to daily plant cycles of photosynthesis. The only time turbulence will work against you is when you are already using CO2 injection. In that case, increasing turbulence will only work to off-gas this additional CO2."

I was always under the impression in a low tech walsted style tank or Tom Barr non co2 type tank that water disturbance should be pretty much minimal if at all to preserve what little co2 is already in there.  I've ensured for the past year my low tech had almost zero water turbulence but if the above statement is true then ill go for this on my second low tech I'm due to start. 

Opinions anyone?? 


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## jack-rythm (2 Jan 2013)

I made a fair few walstads in the past and all my tanks have had no filters, power heads or water pumps or air pumps.. I have had very good results looking back at this. However I was contemplating at one point, installing a very small water pump. My reasoning behind this was to form a little flow circulation to counteract the film residue that would collect at the top. I also believe that agitating the waters surface is better for the tank overall. Having said this I never got round to installing it.  6-7 months down the line its fine. I think its a preference and a situation only the tank owner can answer. If your tank is fine why mess with it? If you are seeing signs of deficiencies due to poor flow etc, then install a small water pump from ebay for a couple quid. I read a lot about certain strategies and tips from other tank users etc about the best methods and best apparatus to buy etc. But I think its important we all are aware that each and every tank is very very different. Requirements will alter and subsequently so will plants health based on our own set ups. In my walstads I have had some excellent growth from stem plants like polysperma and rotala and doubt I could grow them that well in my other filtered bigger tank. Their maybe issues I could improve but looking back at it I didn't need to play with something that was already great. 

Hope that helps mate  Just a few words for thought


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## Iain Sutherland (2 Jan 2013)

Hey al, makes sense to me, if O levels increase with surface movement then no reason for C not to aswell..?
I found that my riccia struggled or was very slow in my nano until i added the eheim liberty  which creates good surface movement and air stone for CRS, after that it went great guns. Also in the tribute which has no flow the HC will grow straight up if i dont water change every 2-3 days, yet carpets if i do so guess that C levels drop too low (for HC at least) after a few days... Totally anecdotal though and assumption is the mother of all...


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## foxfish (2 Jan 2013)

Using that theory - wouldn't simply operating an air stone powdered from an external air pump supply C02 from the atmosphere as well as oxygen?


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## dw1305 (2 Jan 2013)

Hi all,


> "The second is increasing turbulence. There are arguments for and against this, but for tanks without CO2, turbulence should increase both oxygen (O2) and CO2 for your plants. Turbulence works by allowing better gas exchange between the air and the water and, as concentrations of CO2 are generally higher in the air than in the water, creating turbulence or adding an airstone will increase the dissolved concentration of CO2. This will also increase dissolved O2, which livestock, bacteria, and plants also require to thrive. It will also prevent CO2 and O2 levels from undergoing excessive fluctuations within the tank due to daily plant cycles of photosynthesis. The only time turbulence will work against you is when you are already using CO2 injection. In that case, increasing turbulence will only work to off-gas this additional CO2."


It's true, in fact am I the author? from an earlier version of <plecoplanet: Aeration and dissolved oxygen in the aquarium>?


> Using that theory - wouldn't simply operating an air stone powdered from an external air pump supply C02 from the atmosphere as well as oxygen?


Yes it would, but what you have to remember is that there is approx. 400ppm CO2 in the atmosphere and 21% O2, this means that even if we take into account the higher solubility of CO2 compared to O2, the 30ppm CO2 you add to the high tech. tank is about X40 what you would get from diffusion from the atmosphere. Typical CO2 levels in low tech. tank water are dependent upon temperature, pressure and the carbonate content of the water, but should be in the range of 1 – 2ppm (at sea level, at 27oC, pure H2O is saturated with 7.9 mg / l O2, but with only 0.42 mg / l CO2).

cheers Darrel


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## foxfish (2 Jan 2013)

So how do you separate CO2 from O2?
Would it be possible for the hobbyist to harvest enough CO2 from the atmosphere in some way ?


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## dw1305 (3 Jan 2013)

Hi all,


> Would it be possible for the hobbyist to harvest enough CO2 from the atmosphere in some way?


 I think the answer to that one is a probable no, although you can generate CO2 really easily by either biological (yeast and a substrate) or chemical (any carbonate and a strong acid or carbon electrode) processes.

Storing it would be more of a problem. The great thing about FE or Pub gas cylinder is that a huge volume of gas has been pressurised and liquefied all ready (if you think about it a 5kg FE must contain a huge volume of gas).

cheers Darrel


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## Alastair (3 Jan 2013)

So darrel on my new bigger puddle I don't have to worry about the off gassing at all then as its a very low tech anyway I'd actually be introducing extra co2 if I have the water surface slightly agitated then?? 


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## dw1305 (4 Jan 2013)

Hi all,


> So darrel on my new bigger puddle I don't have to worry about the off gassing at all then as its a very low tech anyway I'd actually be introducing extra co2 if I have the water surface slightly agitated then??


 Yes, in a wide shallow tank you will have a large surface area to volume ratio purely by geometry, meaning that even minimal surface movement should ensure optimal gas exchange.

You can't give an absolutely definitive answer for every situation, but assuming that you don't have a huge fish load (which will respire CO2) or extremely carbon rich substrate (something like a garden soil/peat mix that will support a large microbial biomass that will produce CO2) then a larger surface area to volume ratio will mean that you will have more CO2 in the tank water via diffusion. Same applies for all the other gases, they will equilibrate with atmospheric levels fairly quickly.

cheers Darrel


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## BigTom (4 Jan 2013)

Darrel pretty much covered it all, but to put your mind at rest I have quite a lot of surface movement these days Alastair and plants seem to be doing better than ever.


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## tim (4 Jan 2013)

Thanks for the info in this thread very interesting


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## Alastair (4 Jan 2013)

dw1305 said:


> Hi all,
> Yes, in a wide shallow tank you will have a large surface area to volume ratio purely by geometry, meaning that even minimal surface movement should ensure optimal gas exchange.
> 
> You can't give an absolutely definitive answer for every situation, but assuming that you don't have a huge fish load (which will respire CO2) or extremely carbon rich substrate (something like a garden soil/peat mix that will support a large microbial biomass that will produce CO2) then a larger surface area to volume ratio will mean that you will have more CO2 in the tank water via diffusion. Same applies for all the other gases, they will equilibrate with atmospheric levels fairly quickly.
> ...



Thanks for that darrel a great help as always. I can raise my outlets a little now then which should benefit the shrimp too. 



BigTom said:


> Darrel pretty much covered it all, but to put your mind at rest I have quite a lot of surface movement these days Alastair and plants seem to be doing better than ever.



Tom, are you using garden soil under your substrate as before then by the way??? 



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## BigTom (4 Jan 2013)

Yeah, using a mix of Westland's aquatic compost and that blue bag stuff, with a bag of extra grit thrown in to improve aeration because it's 6 to 8 inches deep in places. Capped with sand.

Get quite a lot of what I'm guessing is CO2 bubbling up from time to time.


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## Alastair (4 Jan 2013)

BigTom said:


> Yeah, using a mix of Westland's aquatic compost and that blue bag stuff, with a bag of extra grit thrown in to improve aeration because it's 6 to 8 inches deep in places. Capped with sand.
> 
> Get quite a lot of what I'm guessing is CO2 bubbling up from time to time.



Thanks mate. I've got 3 bags of the pond aqua soil (60 litres) then ill cap it off with the Ada and Columbo but atleast I can have more surface movement now if it helps bring in both co2 and O2. 


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## dean (8 Feb 2013)

Was in an importers the day and there's one tank that has an internal filter thats blasts air into the tank, no ferts have ever been added and the  java fern literally fills the whole tank


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## dean (8 Feb 2013)




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## dw1305 (8 Feb 2013)

Hi all,


dean said:


> no ferts have ever been added and the java fern literally fills the whole tank


Moss have very low productivity levels (just really means they can't grow very quickly), so that the levels of nutrients in any water are likely to be sufficient for growth. Same with light, they will have very low compensation points and their photo-systems may be damaged by high light levels.

The moss would grow more quickly with non-limiting CO2 and nutrients, but the growth gain is going to be small, and conditions will then favour other "photosynthetic organisms" with higher potential productivity. As you ramped nutrients and CO2 up I would predict a green algal bloom, and nobody wants Java moss with hair algae in it.

cheers Darrel


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## BigTom (8 Feb 2013)

dw1305 said:


> Hi all,
> 
> Moss have very low productivity levels (just really means they can't grow very quickly), so that the levels of nutrients in any water are likely to be sufficient for growth. Same with light, they will have very low compensation points and their photo-systems may be damaged by high light levels.
> 
> ...


 
Darrel, we'll forgive you because it was 5.30 on a Friday, but the post was about Java fern, not moss


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## dw1305 (8 Feb 2013)

Hi all,


BigTom said:


> Darrel, we'll forgive you because it was 5.30 on a Friday, but the post was about Java fern, not moss


Mmmmm, I did wonder about the pictures after I'd posted. Same applies for ferns as for mosses, though low potential growth rate even with added CO2 and nutrients, although they will show a great response than the mosses would.

cheers Darrel


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## dean (9 Feb 2013)

dw1305 said:


> Hi all,
> 
> Mmmmm, I did wonder about the pictures after I'd posted. Same applies for ferns as for mosses, though low potential growth rate even with added CO2 and nutrients, although they will show a great response than the mosses would.
> 
> cheers Darrel



I think it's chill out time for you matey 

I agree with what you say, just thought a pic would prove the theory


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