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Do I need to add CO2 when using aquasoil?

Mitchel

Mitchel

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Can you answer please a noob question?

Do I need to add CO2 when using aquasoil?
Beqause in my tank I use aquasoil. It has a pH of 6.8 and the KH is 5. So I would have about 24ppm CO2 in the water. That seems sufficient for plant growth.
So, do I need to add extra CO2 in gas form?


cheers,

Mitch
 
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Mitchel said:
Can you answer please a noob question?

Do I need to add CO2 when using aquasoil?
Click to expand...

No, the chosen substrate and CO2 injection are mutually exclusive. You can use aquasoil on a low energy tank just as you can use CO2 with a pure sand or gravel substrate. It just comes down to personal preference.

Mitchel said:
Beqause in my tank I use aquasoil. It has a pH of 6.8 and the KH is 5. So I would have about 24ppm CO2 in the water. That seems sufficient for plant growth.
Click to expand...

You won't have 24ppm of CO2 in your tank if you are not injecting CO2, you will likely have less than 3ppm. I assume you have gleaned that value from a pH/KH table, put that is misleading as it assumes pure water samples - there are other acids in you tank coming from the soil and other organic compounds that will be lowering your pH. With a KH of 5 you would typically expect a pH well over 7.

A large number of plants will grow perfectly happily without CO2 injection. Their growth will be slower (for most species), which can be beneficial in terms of ease of tank management.

Mitchel said:
So, do I need to add extra CO2 in gas form?


cheers,

Mitch
Click to expand...

No, you don't 'need' CO2 unless you have some plant species that specifically benefit from it. Adding CO2 is something that should really be planned for from the outset of designing a tank so you are ready for the accelerated plant growth, increased maintenance and can ensure things like adequate flow and CO2 distribution can be achieved in the tank layout.
 
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Wookii said:
the drop checker
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I thought exactly the same, though I honestly don't think Mark is fraudulent in any way.

I suspect, no stronger, using soft water and acidic nutrient rich compost with I guess lots of woody/carbon rich material and inoculated I assume with various types of bacteria he generated more CO2 from decomposition than we might expect, hence all the white mould at the early stages, but I would have thought a maximum of 15 ppm, so I would expect the indicator to be less brightly green, but really I'm hopeless describing shades of green. I aim for <20 ppm of CO2 in my tank, but I think now, having scrutinised and squinted at my drop checker with a torch, I'm hitting 25-30 ppm at times, but I am injecting. But with the right compost and soft water?

My small tank, KH <5, if the CO2 runs out it does not go blue, it stays a dark green, maybe a slightly purplish colour, my main tank KH <10, never <8, blue is the colour within 24-36 hours of CO2 running out.

But glad you found it interesting, I won't tell your boss!
 
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Hi all,
Connswater said:
I suspect, no stronger, using soft water and acidic nutrient rich compost with I guess lots of woody/carbon rich material and inoculated I assume with various types of bacteria he generated more CO2 from decomposition than we might expect
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It would have to be a huge amount, because the <"rate of out-gassing"> would be dependent on the concentration gradient of dissolved CO2 in the water and and the level of CO2 in the atmosphere.

You would also need to supply a similarly large amount of oxygen (to support aerobic decomposition), fine why the light is on, but after lights out? Curtains for the livestock.

cheers Darrel
 
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dw1305 said:
Hi all,

It would have to be a huge amount, because the <"rate of out-gassing"> would be dependent on the concentration gradient of dissolved CO2 in the water and and the level of CO2 in the atmosphere.

You would also need to supply a similarly large amount of oxygen (to support aerobic decomposition), fine why the light is on, but after lights out? Curtains for the livestock.

cheers Darrel
Click to expand...

Plus that much plant mass would gobble up any CO2 produced by the system under that lighting.

Simon Cole said:
I am guessing that the ambient concentration of CO2 is quite high in the room because he has like 7 injected tanks and must be working it there a lot. Not sure whether that would have much of an effect.
Click to expand...

Interesting idea - I wonder what the atmospheric levels would have the be to achieve circa 5-7ppm (judging by that drop checker colour)? Probably quite a worrying level! . . . I bet Darrel knows how to calculate it - @dw1305 ?
 
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Ratvan said:
At 18.23 he notes the colour of the drop checker

"Combination of the substrate and the respiration of the fish..."
Click to expand...

I just can’t see that being enough to effect a drop checker colour, unless you got some organic compost style substrate that decomposing at a decent rate.
 
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Wookii said:
I wonder what the atmospheric levels would have the be to achieve circa 5-7ppm (judging by that drop checker colour)? Probably quite a worrying level! . . .
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From here in the range of 4000 ppm atmospheric CO2. I thought it interesting that he didn't notice a green drop checker until after he added the fish, so I'd guess their respiration is a big part of it.
 
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Andy Pierce said:
4000 ppm
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Having taught for too long to detail, at that sort of level, the >2500 ppm not only did students fall asleep but teachers were perfectly capable of boring themselves into a slumber, the point at which the window definitely needed to be opened to shake everybody out of a slumber, or was I just especially boring?
 
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Wookii said:
Interesting idea - I wonder what the atmospheric levels would have the be to achieve circa 5-7ppm (judging by that drop checker colour)? Probably quite a worrying level! . . . I bet Darrel knows how to calculate it - @dw1305 ?
Click to expand...
Andy Pierce said:
From here in the range of 4000 ppm atmospheric CO2. I thought it interesting that he didn't notice a green drop checker until after he added the fish, so I'd guess their respiration is a big part of it.
Click to expand...
Alternatively, it could have been a larger water change with CO2 in it.
I have measured CO2 levels in my well-insulated bedroom with closed windows and door above 2000 ppm, even close to 3000. I don't know, maybe in a basement with not much ventilation, running multiple CO2 tanks (or fermenting wine in a few barrels) could do surprising levels of CO2.

I am not a color expert (but rather a color blind), but if the drop checker is green, and if I am not wrong, the CO2 levels should already be at least above 10 ppm.
dw1305 said:
You would also need to supply a similarly large amount of oxygen (to support aerobic decomposition), fine why the light is on, but after lights out? Curtains for the livestock.
Click to expand...
This. Without O2 supply, I don't think much CO2 can be produced. The maximum solubility of oxygen in the water is quite low, I don't think there is enough to support 10 ppm+ CO2 production. And if oxygen is taken up from the air, CO2 should be also out-ventilated, unless there is a lid on the aquarium with a headspace over the water.
Wookii said:
Plus that much plant mass would gobble up any CO2 produced by the system under that lighting.
Click to expand...
True, therefore the oxygen supply for CO2 production could not come from the plants.

Fish will also not produce this much CO2 without using similar amounts of O2, at least not for long.

So in summary, I assume a cleanup session and a larger water change a few hours before taking the video.
 
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If he's got 0 KH as indicated (RO water + APT Sky) and the drop checker is very dark blue-ish green, what ppm CO2 is that supposed to be? Is there a definitive chart on this? This is not my really my area.

I can't comment on the actual amount of CO2, but this seems like it is functionally similar to Sudipta Shaw's tanks only with easier plants. Perhaps the soil is optimized to have more organic material

Connswater said:
And perhaps this:

15.10. Hybrid Low Tech Planted Aquarium

This type of planted aquarium uses wood pellets in the substrate to create carbon dioxide for the plants.
aquariumscience.org aquariumscience.org
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I am generally suspicious of Aquarium Science especially when it comes to plants, but I admit I think there may be something to using organic material that is recalcitrant to decomposition in a substrate for a non-injected tank. I have done something similar myself with pine bark fines, and I still am working up a write up on it. But the pine fines are just one component in my mix; using all wood chips and sand seems a bit nuts to me. I'm not clear that any of the pictures on that page are using this substrate, so it's impossible to evaluate.

But no, you don't have to use CO2. 😉
P8260408.JPG
 
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Hi all,

Andy Pierce said:
From here in the range of 4000 ppm atmospheric CO2.
Click to expand...
5-7 ppm CO2 in water diffusing into air would indeed mean 4000 ppm, which matches my calculation sheet, below in 'set 5'. 4000 ppm is roughly 10x more than ambient CO2 and outside any healthy range...
1738855196366.png
Please note:
1. Diffusion takes time, which can be speed up by lots of (surface) flow and aeration or slowed down by absence of it.
2. A closed lid could mean a vastly different ambient CO2 than in the room itself.
3. As mentioned already, it does not take in account the (an)aerobic respiration of alle organisms in the tank! And for a densely packed planted tank with reasonable amount of livestock and a organic soil this might be very substantial. And the delta of O2 and CO2 would be different for each tank, I guess. And higher temperatures mean higher metabolism.
4. And warmer water takes up slower and less CO2 (see the differences between set 1 and 3) and oxygen.

So there are a lot of factors on the CO2 level and underexperienced in chemistry of organic soil break down to say whether 5-7 ppm is achievable. And I even know less about oxygen levels in a unaerated tank during 24 hours. What I can confirm that my dutch tap water consists 6 ppm of CO2 without exception.

For item 3, I am not aware of any quantified figures like in-/uptake of oxygen and/or CO2 within and outside the photosynthesis period. Does anyone know of such experiments? The upcoming months I will conduct those in my own display tank with a CO2 and O2 monitoring device (aka the Aqua Gas Sensor) next to pH monitoring.

In my tank with decent amount of aeration, CO2 usually fluctuates between 1.3 and 1.9 ppm, depending on the time of day and presence of humans around the tank / in the room. Which I can show you people is the effect of absence of CO2 by human presence in the room, as we went for a trip of a few days with the family.
- The overall trend of CO2 in the water (see graph in yellow) is going down as the days go by.
- And watch the CO2 go as we came back (visible with the green line) on the 30th of December around 16:00 hours, even when light were still on (line in blue).
- A nett diffusion and respirational effect on CO2 during the night can be seen, as it goes up roughly 0.15 mg/L.
I will test the effect by aeration too, by shutting it down for 48 hours. It might creep up higher during the night as ambient CO2 is low so drives out the CO2 from the water. But during the day it might plummet lower as human CO2 won't be diffused into the water quite as fast as with aeration.

1738868872512.png

I'll stop rambling now...
Cheers!
 
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