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Lean dosing pros and cons

Tim Harrison

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If I had to speculate I would say it's beneficial to do WC during the photoperiod since plants would be exposed to atmospheric CO2 which they can capture and store in their leaves. Josh made a comment in that regard and I would tend to agree.
I think that's pretty much the nub of it. Aquatic plants adapted to life under water will be pretty good at absorbing gases from the atmosphere. So when they're exposed to 410ppm CO2, as opposed to 10ppm in water, via a daily water change you bet they're going to do okay, so no great mystery.

And I'm guessing they'll most likely store atmospheric gases in their aerenchyma to be used later on in the photoperiod upon re-submergence. This method of getting CO2 in to aquatic plants is nothing new I remember reading about it way back, not sure where, probably the Barr Report.
 

Sudipta

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This method of getting CO2 in to aquatic plants is nothing new I remember reading about it way back, not sure where, probably the Barr Report.
I think you are referring to this. I was quite surprised last year when the plants did really well in relatively high temperature in one of my non-CO2 supplemented softwater tanks since I was changing water every day for 3 weeks due to ich issues. However, it made a lot of sense after I read Tom's post and also from a conversation with him.
 

Gorillastomp

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Isn't pearling associate with the fact that you add fresh water high in dissolved oxygen ?

Because i make water change using my tap which comes from a well. I doubt this water is high in co2 and change water by the overflow method. I get mad pearling as well after a wc.
 

Hanuman

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Isn't pearling associate with the fact that you add fresh water high in dissolved oxygen ?
Pearling is associated with plant consuming CO2 and producing/perspiring O2.

Because i make water change using my tap which comes from a well. I doubt this water is high in co2
I can't tell you for sure about your water specifically but typically well waters can have a very high CO2 content. So that is probably why you see lots of pearling specially if you have adequate amounts of light.
 

dw1305

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Hi all,
How would you know this? My water is out at PH 8.3-8.4, if i let it sit a day its comes down to around 8.2 - 8.3.
It can be a temperature (and / or) pressure effect. All dissolved gases are more soluble at lower temperature (and higher pressure), which means that if you do a 50% water change with cool water all that "spare" dissolved gas will come out of solution as the water warms.

In this case most of "pseudo pearling" the bubbles will be nitrogen (N2), purely because the atmosphere is ~70% nitrogen.

Water (at 25oC) holds, a maximum of, ~13 mg / litre dissolved N2 and 8 mg / litre oxygen (O2), everything else (CO2, Argon (Ar) etc) are just traces.

cheers Darrel
 
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_Maq_

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He does two very large water changes (>80% by the looks of it) per week, and so adds a good amount of dissolved CO2 to the system at those points...
Tap water, due to elevated pressure, often contains lots of dissolved air. There's no reason to expect significantly elevated content of CO2 from this source.
However, if a well water is the source, it may very well contain high levels of CO2. In lower parts of many wells CO2 rich atmosphere is the norm => partial pressure of CO2 is higher => water is full of CO2.
 

Wookii

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Tap water, due to elevated pressure, often contains lots of dissolved air. There's no reason to expect significantly elevated content of CO2 from this source.

But air contains in excess of 400ppm CO2, so if that water has “lots of dissolved air” in it, it will be naturally much higher in dissolved CO2 than water that is in CO2 equilibrium with the air. This can be shown fairly easily by measuring the pH increase after allowing tap water to degas.
 
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_Maq_

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But air contains in excess of 400ppm CO2, so if that water has “lots of dissolved air” in it, it will be naturally much higher in dissolved CO2 than water that is in CO2 equilibrium with the air. This can be shown fairly easily by measuring the pH drop after allowing tap water to degas.
Will you explain? I think if I leave the tap water to degas, CO2 content would decrease, and pH would rise, as a result. Am I missing here something?
 

Wookii

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Will you explain? I think if I leave the tap water to degas, CO2 content would decrease, and pH would rise, as a result. Am I missing here something?

Yes, you’re missing the train of the conversation which is about the video of the low tech tank in post #1147 and possible explanations as to how the person running the tanks was achieving apparent ‘high tech’ growth on a ‘low tech basis’. One of which was increased CO2 levels by daily water changes.

You also have to appreciate that whilst you might wait 24 hours for your water change water to degas, most don’t and go straight from tap to tank via hose or bucket.
 

_Maq_

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But my question remains unanswered: Will you explain? I think if I leave the tap water to degas, CO2 content would decrease, and pH would rise, as a result.
 

Gorillastomp

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Ita depends of your water supply, mine PH goes down if i let it sit on counter. That would mean my water supply is really low in dissolved co2. I use Well water.
 

Wookii

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But my question remains unanswered: Will you explain? I think if I leave the tap water to degas, CO2 content would decrease, and pH would rise, as a result.

Explain what? Your statement is correct, but not relevant to what is being discussed?
 

_Maq_

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But air contains in excess of 400ppm CO2, so if that water has “lots of dissolved air” in it, it will be naturally much higher in dissolved CO2 than water that is in CO2 equilibrium with the air. This can be shown fairly easily by measuring the pH drop after allowing tap water to degas.
If pH drops on degassing, it's not the proof of what you are saying - that the tap water would be naturally much higher in dissolved CO2. It would be a proof of the opposite.
 

_Maq_

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So it was a misunderstanding, @Wookii. I never happened to check my tap water afresh and then a few hours later. Did you? What was the result?
 

sparkyweasel

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It can be a temperature (and / or) pressure effect. All dissolved gases are more soluble at lower temperature (and higher pressure), which means that if you do a 50% water change with cool water all that "spare" dissolved gas will come out of solution as the water warms.
Which is why we sometimes get 'pearling' on hardscape, glass walls, filters etc.
 

Wookii

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So it was a misunderstanding, @Wookii. I never happened to check my tap water afresh and then a few hours later. Did you? What was the result?

I have some time ago - I’m an RO user not tap so haven’t measured recently, but digging out the pH meter to run a test just now for the purposes of this conversation:

Water fresh from the tap:

69CEBD3B-B586-41C7-B3A9-EC4797157A9E.png



Water from the same tap that’s been standing for a good 12 hours+:

944567FB-BC60-4A09-9432-9425E166F038.png


Taken with a calibrated Hanna Halo HI11102.

Alkalinity at this time of year approximately KH7 give or take.

Someone smarter than me can probably estimate the difference in dissolved CO2 that could be accounting for the difference in pH, but the overriding point being at an approximate pH0.7 difference it’s not an insignificant amount of additional dissolved CO2.
 

_Maq_

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Someone ... can probably estimate the difference in dissolved CO2 that could be accounting for the difference in pH
Some 28 ppm decreased to 5 ppm. But it strongly depends on alkalinity.
Still, it's a strong argument that you're right - and I was wrong - in that a fresh tap water can contain remarkable amount of CO2. Wow!
 

Hanuman

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in that a fresh tap water can contain remarkable amount of CO2. Wow!
Indeed it does and that's a fact. Tap water can contains a good amount of CO2 due to how the water is processed in water plants before it is sent back into the pipes. This is not intentional but a consequence of the water treatment processes.
 
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