# CO2, carbonates and water clarity



## dmachado (24 Oct 2013)

For a long time I have seen a direct connection between water clarity and the amount of CO2 that is dissolved in water. 

Newly mixed yeast bottles increase CO2 and the water becomes crystal clear, towards the end of their production more and more particles become visible, I add a new bottle and the water becomes crystal clear again.

I also have found that biocarbonates are a good carbon supplement when CO2 is less than ideal or not present at all. When I throw 1 or 2 tea spoons of baking soda in the aquarium, water clarity improves dramatically in the next hours. This is a sign that carbon in the form of carbonates is available for the plants and is being used.

What are these particles and how is their visibility related to the carbon uptake of my plants? 

What is the preference/ease of uptake plants have for CO2 over bicarbonates? 5:1? 10:1?

Is there another source of carbon I should be trying (still avoing going to pressurized CO2)?


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## Yo-han (24 Oct 2013)

You can always try liquid carbon like excel/easycarbo. I don't know the preference ratio, but I do know it takes more energy to use bicarbonate as carbon for a plant. I think if CO2 is available it will always be preferred.

I don't really get the particle new bottle effect. I do know Amano uses the diffusor because the small bubbles collect very tiny suspended particles in the water, making one bigger particle which is trapped in the filter more easily (flocculation). But I'm sure someone else has a better explanation!


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## ceg4048 (24 Oct 2013)

dmachado said:


> What is the preference/ease of uptake plants have for CO2 over bicarbonates? 5:1? 10:1?


It's important to understand that plants do not uptake bicarbonate.

Bicarbonate cannot be used directly because, in the first place, HCO3- is not able to diffuse across external cell boundaries very easily. CO2 and O2, on the other hand pass easily across animal and fish cell walls. In the second place, the Carbon fixing mechanism known as The Calvin Cycle, is a series of redox reactions that convert CO2 , and ONLY CO2 into starch. HCO3- would not work in these reactions as they are specifically tuned to CO2. ALthough there are alternate Carbon fixing mechanisms, such as C4 and CAM, none of these can be initiated without CO2.

Plants that have the ability to indirectly use HCO3- do so by converting  it to CO2 and then uptaking the CO2 as described in the post What form of carbon do water plants use? | UK Aquatic Plant Society

HCO3- processing is very expensive, and so in the presence of good CO2 the process is usually disabled. When the CO2 is low or marginal the HCO3- mechanism is initiated, so the question of preference has an obvious answer.

CO2 helps to clarify the water by enhancing the photosynthetic rate in plants, which then improves the Oxygen levels in the tank. Aerobic bacteria are able to break down the complex organic waste molecules, which are more visible, into simpler molecules which are more transparent than the larger complex molecules.

Cheers,


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## dmachado (24 Oct 2013)

Excellent! Many thanks for your explanation!


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## GreenNeedle (24 Oct 2013)

Clive beat me to it.  I was going to say it's not CO2, it's O that improves clarity.  Just letting the water ripple has the effect on clarity so as Clive says plants producing more O achieves this somewhat


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## ian_m (24 Oct 2013)

If carbonate could be used for plant carbon, we would all be adding .....carbonate, potassium, sodium, calcium etc. But we are not, so clearly not a replacement for CO2 gas or inferior liquid carbon.


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## GreenNeedle (24 Oct 2013)

Plants can use carbonate but it is very inefficient and is a last resort for the plants.  Will not provide enough to calm worries of algae either.  Leonardite under the substrate 





ian_m said:


> If carbonate could be used for plant carbon, we would all be adding .....carbonate, potassium, sodium, calcium etc. But we are not, so clearly not a replacement for CO2 gas or inferior liquid carbon.


 
Just to be cheeky there are loads of plants that can use carbonates as carbon source.  Just that it is not ideal and they will only seek out carbonates if there is no CO2   However it would not be a great idea to assume that you could select said plants forget about CO2 and pour the carbonates in.


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## dmachado (25 Oct 2013)

ian_m said:


> If carbonate could be used for plant carbon, we would all be adding .....carbonate, potassium, sodium, calcium etc. But we are not, so clearly not a replacement for CO2 gas or inferior liquid carbon.


 

My point was: when DIY CO2 gets weaker, carbonates are a reasonable "backup plan" for many plants, even at higher expense. Not everyone is running pressurized CO2, either for economical, safety or whatever reason. I found there is a connection, new for me but not for others. This is not about potassium, calcium and sodium. I also read about CO2 uptake through the root system, which explains the excellent performance my previous 150L setup had, with mineralized bonsai substrate, no CO2 addition except some easycarbo on water changes, PLUS baking soda.



SuperColey1 said:


> Plants can use carbonate but it is very inefficient and is a last resort for the plants. Will not provide enough to calm worries of algae either. Leonardite under the substrate
> 
> Just to be cheeky there are loads of plants that can use carbonates as carbon source. Just that it is not ideal and they will only seek out carbonates if there is no CO2  However it would not be a great idea to assume that you could select said plants forget about CO2 and pour the carbonates in.


 
My last setup had a very fast growing plant mass which was lit by 80W T5 and the only algae I had was cladophora in low water flow areas. Most of those plants are "carbonate friendly", sagitaria, vallisneria, green and red tiger lotus, cryptocorine, etc. This new setup, although twice the volume and half the lighting, has yet to stabilize and seems more demanding, and I'm not thinking of stopping CO2 injection. In fact I am close to control the night shut-off for DIY CO2.

I will keep adding baking soda and try to improve DIY CO2.


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## dmachado (8 Jul 2014)

I just managed to control my DIY CO2 using a solenoid and a garden sprayer which has a safety relief valve. Now I can inject 24 hours worth of CO2 production, instead of wasting 2/3 while the lights are off.






When the solenoid opens, the bell above the powerhead fills with CO2, and this is mixed in the water inside the bell or pulled into the powerhead and "shredded" by the impeller.





You can see the CO2 level close to the powerhead's intake (it's upside down). Any CO2 that exceeds that mark, gets pulled into the impeller, this happens mainly just after the solenoid opens.

I am improving DIY CO2 recipes, more on that later.


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## NatureBoy (8 Jul 2014)

when plants use carbonates the leaves usually get heavy with precipitated calcium carbonate = pretty ugly look. The process by which this happens is called biogenic decalcification


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