# Question for ceg4048



## Jose (4 Mar 2015)

Hi everyone,

This is an extract of the article on CO2 by ceg4048,

"The relationship in practical terms therefore is that if Hobbyist "A" has tap water measuring ph 7.2 and kH 10 ( high levels of carbonate and bicarbonates) then 30 ppm of dissolved CO2 may only cause his pH to drop to 7.0

Conversely, Hobbyist "B" has tap water also measuring 7.2 but kH 6. More acid can form in his water (because of less carbonate and bicarbonate levels), so 30 ppm dissolved CO2 in his water will result in a pH drop to 6.8."

Ok Id like to understand this better because Im a bit confused. I thought that to get 30 ppms (or any ppm of CO2) the change in pH would have to be the same (e.g 1(aprox) for 30 ppm) no matter what KH the water is. This is what I understood from Tom Barr.

So to understand this better:
Hobbiest A, water of KH 10, His pH would drop 1 unit.
Hobbiest B, water of KH  6, His pH would drop 1 unit as well.

To get another ppm of CO2 the water would change X units of pH, but it should be the same X amount for a different water with another kh.

We can check this with the pH-KH table. You can try doing it with two different kh waters. The result is that the change in pH is the same for both if we have same co2 ppm. I know ph kh tables dont work very well for real waters but for this comparison its appropriate, I would've thought..

What am I missing?

Thanks all!!


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## markk (4 Mar 2015)

Jose said:


> What am I missing?



Hi Jose,

I won't even attempt to give you the specific science, but bear in mind that the key issue is that water with a higher kH has more buffering capacity - hence more CO2 is required for a given pH change.

I'm not sure which ph/kH tables you've been looking at but the numbers you've quoted above seem to tie in with these charts:-

http://www.barrreport.com/forum/barr-report/co2-enrichment/11862-co2-ph-kh-table
http://www.practicalfishkeeping.co.uk/content.php?sid=5264#
http://www.gpodio.com/co2_chart.asp

(if anything, the pH drop for the water with 6 kH is a little understated - in theory!)

regards

Mark


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## Jose (4 Mar 2015)

markk said:


> (if anything, the pH drop for the water with 6 kH is a little understated - in theory!)



Thanks for replying Markk,
No nevermind the exact numbers. Its all about the idea. Ive read those Tom Barr posts but Ill read through them again see if I can find exactly what I mean (unless I misunderstood)


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## Jose (4 Mar 2015)

markk said:


> I won't even attempt to give you the specific science, but bear in mind that the key issue is that water with a higher kH has more buffering capacity - hence more CO2 is required for a given pH change.



More CO2 is needed but the X amount of CO2 *dissolved* changes pH in the same Y ammount no matter what hardness the water (theoretically)


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## Rahms (4 Mar 2015)

Jose said:


> More CO2 is needed but the X amount of CO2 *dissolved* changes pH in the same Y ammount no matter what hardness the water (theoretically)



I'm not really familiar with the science here, but looking at the tables I can say this statement is dangerously on the verge of being wrong . The change in ppm is not linear.  Going from 3ppm to 30ppm (27ppm increase) is always going to drop your pH by 1, yes.  However, dropping your pH by 2 will not take you to 57 ppm (i.e. 3ppm+27ppm+27ppm), it will take you to 300ppm.  The example in your first post has different starting ppms on that table.

It seems to imply "hobbyist A" has tapwater coming out at 18.9ppm CO2 though! I think it's saying that until he doses above 18.9ppm he will simply be displacing something else (carbonates?), so there will be no pH change even though his dissolved CO2 is increasing.  That or its an unrealistic example and his water would be coming out at closer to 8 pH!


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## Jose (4 Mar 2015)

All starting points are from equilibrium with air.


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## Rahms (4 Mar 2015)

Jose said:


> All starting points are from equilibrium with air.



Not really sure where this fits in with what I said. It's just... a fact.


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## EnderUK (4 Mar 2015)

Sorry miss understood.

You're thinking of pH as a linear scale. It's not really, it's a log scale.


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## markk (4 Mar 2015)

Jose said:


> More CO2 is needed but the X amount of CO2 *dissolved* changes pH in the same Y ammount no matter what hardness the water (theoretically)



Jose,

I don't believe that is true - although I'll concede I may be either wrong  or just not understanding what you're trying to prove/understand.

Apologies if any of this is pitched at the wrong level (either to technical or too simplistic) - I don't know what your background is.

Firstly, any CO2 that isn't dissolved is irrelevant to pH. Yes - there will be an equilibrium between gaseous and aqueous CO2 but I'm assuming that we're talking about the ppm of *dissolved* CO2.

Secondly, the pH scale is not linear. pH is broadly speaking a measurement of the concentration of H+ ions and the amount of H+ ions needed to drive any given solution from, say, pH 7 to pH 6 is very different from the amount needed to move it from pH 6 to pH 5. Not strictly relevant to your comment above - but it's an important point, particularly when we start comparing movement in CO2 ppm (linear scale) and pH (logarithmic scale).

and thirdly, is buffering again But getting more technical (I had to resort to some revision) - have a look at the equation (and text) on this page:-

http://mbrewer.edublogs.org/2012/03/07/the-carbonatebicarbonate-buffer-system/

CO2 will tend to form carbonic acid in water, which will in turn tend to split into an H+ ion and bicarbonate and the bicarbonate will tend to further split into another H+ ion and carbonate.

For our purposes we pump CO2 in at the left and on the right we get some H+ ions that drive our pH value (but remember the differences in scale). With no other factors in play (lets say it's pure water), there will be a direct relationship between CO2 in and pH 'out' - but the specific pH value is dependant on the balance of the different equilibria in the equation referenced.

But if you now add some Sodium bicarbonate or Potassium bicarbonate, these will raise your kH and in aqueous solution will disassociate and add bicarbonate and carbonate to your solution - i.e. 2 of the same molecules that are already at play in the CO2 equilibria above. These will push the balance of that equilibria to the left - hence reducing the number of H+ ions and increasing the pH. The more (bi)carbonate you add, the more you will shift the balance.

Approaching it from the other direction, if I start with a solution of 'high' kH, I have to add much more CO2 on the left to achieve the same number H+ ions on the right (i.e. lower the pH) - as the relatively high levels of (bi)carbonates will tend to 'absorb' them. 

Hopefully I've got that right - and not gone off on a complete tangent! (but the revision was useful to me at least)

Cheers

Mark


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## Jose (4 Mar 2015)

Sorry guys but hopefully someone will answer my question since it hasnt been by now. Ill give a clearer example hopefully. So guys grab a ph kh table.

Tank number 1: kh=10
If we take water from it and let it equlibrate with the atmosphere in a glass it will give a ph reading of around 8.3 and the co2 ppm will be around 1.5 (its just an example dont get hung up on numbers please) and this is just water + carbonates. All data is extracted from the table.
Now we inject co2 until we have 30 ppm and the ph should drop to around 7. This is a 1.3 units ph drop.

Tank number 2: kh=15
We do the same, put it in a glass and let it reach equikibrium. Ph should read around 8.5 with 1.5ppm of co2 again.
Now we add co2 once more until 30 ppm and ph should read around 7.2 (from chart) This is again a ph drop of 1.3 units.

In both cases(kh 10 and kh 15) ph dropped 1.3  units to get 30 ppm co2 dissolved. So we need the same ph drop independently of kh( hardness) to get to a certain co2 ppm.

This are all numbers extracted from the ph kh chart. The only suposision I made is the co2 ppm for equilibrium. This might not be 1.5 ppm of co2 but its irrelevant what the exact number is really.


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## Rahms (4 Mar 2015)

but thats completely different to the original example you posted, ofcourse no-one has answered it.

I acknowledged in an earlier post going 1.5ppm -->30ppm will create the same pH drop *in the table*. But in the original example, the water shows ~11ppm and ~19ppm _from the tap._ So the issue is whether the real-life measurement is accurate at all levels of CO2, or only beyond a certain point, which is what markk was explaining when talking about buffering.


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## markk (4 Mar 2015)

Jose said:


> Sorry guys but hopefully someone will answer my question since it hasnt been by now. Ill give a clearer example hopefully. So guys grab a ph kh table



OK - sorry for the confusion - I see where you're coming from now.

Going back to your original question, ceg4048 just assumed 2 water samples with the same starting *pH* but different kHs.

In your examples you've assumed 2 water samples with the same starting *CO2* but different kHs.

You're both then adjusting the *CO2 *to 30ppm. In ceg4048's case, the change in CO2 is different for each sample (he made no assumptions about CO2 levels at the beginning) but in your case it's the same for each sample.

Just two different uses of the same table - does that help?

regards

Mark


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## Jose (5 Mar 2015)

Yeap I think you guys got it right this time. Well done.

But still You would think that you have to let tap water rest and get to equilibrium to measure pH. This way you can measure the real pH change due to your CO2 injection without the error of the tap CO2. Wouldnt you?
If this is as you say guys then the example is not about kh but about different CO2 concentratiosn from the tap which doesnt make sense.
He is trying to make a point about waters with different kh(I wouldve thought). In one of them you need to change pH more than in the other one. But this is not backed up by the table or is it?
Unless the equilibrium CO2 ppm is different for each water (I dont think its that different).

So, ceg's starting points arent necessarily from equilibrium with the atmosphere? Different kh and same ph just means there is something else in the water other than carbonates. Could be CO2 or not. If its not CO2 then the pH drop should be approx the same (right?).

Cheers!


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## markk (5 Mar 2015)

markk puts his Devil's Advocate hat on



Jose said:


> But still You would think that you have to let tap water rest and get to equilibrium to measure pH.


Why? Th pH is the pH - but see below.



> This way you can measure the real pH change due to your CO2 injection without the error of the tap CO2. Wouldnt you?



But you're injecting CO2 into your tank. The real pH change - the one that is important - is in your tank water. The starting point is your tank water parameters before lights on/CO2 on and the end point is the pH when you reach your desired CO2 levels.

The kH/pH chart is telling you that for higher kH, it gets progressively harder to push the pH below around 7 and for lower kH you can drop below 7 and beyond very quickly if you're not careful.

If, for your water, the pH swing is too high for your livestock, then you need a rethink...



> If this is as you say guys then the example is not about kh but about different CO2 concentratiosn from the tap which doesnt make sense.



The example is about kH, pH and CO2 - it just doesn't care about the starting CO2 levels (or whether it is tap or tank water).



> He is trying to make a point about waters with different kh(I wouldve thought). In one of them you need to change pH more than in the other one. But this is not backed up by the table or is it?
> Unless the equilibrium CO2 ppm is different for each water (I dont think its that different).



Well - it could be. I can't find anything to support this but if you go back to all of those carbonate buffering equilibria, if you have higher kH then you are pushing those equilibria towards the left (CO2 + H2O). This should have an effect on the equilibrium between 'atmospheric' CO2 and dissolved CO2.



> So, ceg's starting points arent necessarily from equilibrium with the atmosphere? Different kh and same ph just means there is something else in the water other than carbonates. Could be CO2 or not. If its not CO2 then the pH drop should be approx the same (right?).



I think they are, as you say, just examples and they are just demonstrating the general concept. They tie in with the 'theory' behind the tables, as do the examples you gave. You just need to remember that they don't care about the starting point of CO2.

regards

Mark


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## Jose (5 Mar 2015)

markk said:


> Why? Th pH is the pH - but see below.



Because this is the only way to get a consistent measurement since co2 in tap water will vary. The idea is to be able to just measure a pH drop when you are fine tuning your CO2. No need to measure kH.



markk said:


> But you're injecting CO2 into your tank. The real pH change - the one that is important - is in your tank water. The starting point is your tank water parameters before lights on/CO2 on and the end point is the pH when you reach your desired CO2 levels.


Exactly the best way to get a starting point of your tank water is from the equilibrium with the atmosphere (glass of water) which will always be the same(aprox). This way you can rule out measuring kh which is a huge source of error.

I think we got to the bottom of it. His starting points are not from the equilibrium with atmosphere but still the question stands if he is comparing khs. pH will need the same jump to get to x ppm of CO2 for different kh waters. This is of course if the starting point is the same one (e.g equilibrium w/o co2 injection). In other words we need our pH to change the same amount no matter what kh., *if everything else is the same *(starting and finishing CO2 ppms). So pH jump (not CO2 volume injected) that we need is independent of water hardness.


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## Jose (5 Mar 2015)

Here are some references to the 1 unit ph change to get 30 ppm CO2. Notice there is no reference to kh.

http://www.barrreport.com/forum/barr-report/co2-enrichment/217799-co2-impact-of-kh-and-kh

here are his exact words from another one:

"Say you have 30ppm CO2 in a KH of 10 and a 30ppm CO2 in a KH of 1.

The pH difference is? 1.0 pH units.

6.0 vs 7.0 pH.

Without adding CO2?
About 7.2 and 8.2"

And the link:
http://www.barrreport.com/forum/bar...1102-different-co2-forms-under-low-vs-high-ph

So....cegs words seem to be at least misleading.


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## markk (5 Mar 2015)

Jose said:


> Here are some references to the 1 unit ph change to get 30 ppm CO2. Notice there is no reference to kh.
> 
> http://www.barrreport.com/forum/barr-report/co2-enrichment/217799-co2-impact-of-kh-and-kh
> 
> ...




This specific quote 





> The pH difference is? 1.0 pH units.


 is referring to the difference in pH between two specific, different kH solutions, both with 30ppm CO2.

The 1.0 is pure coincidence (pick a different kH and check).

The point he is making is that if you take away the extra CO2, and implicitly let it drop back to some sort of 'atmospheric' equilibrium, both solutions will change pH by about 1.2 i.e. the *same*- which is what I thought we were talking about?


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## Jose (5 Mar 2015)

markk said:


> The 1.0 is pure coincidence (pick a different kH and check).



I have done it. Its always around 1 unit pH. Its not coincidence. You arent reading the table properly then.


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## Jose (5 Mar 2015)

markk said:


> The point he is making is that if you take away the extra CO2, and implicitly let it drop back to some sort of 'atmospheric' equilibrium, both solutions will change pH by about 1.2 i.e. the same- which is what I thought we were talking about?



Exactly this is what we are talking about. Are we reading same things?


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## markk (5 Mar 2015)

Jose said:


> I have done it. Its always around 1 unit pH. Its not coincidence. You arent reading the table properly then.



for CO2 @ 30ppm

- kH 1: pH = 6.0
- kH 4: pH = 6.6

Have I got that wrong?

or do I need some fresh air


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## Jose (5 Mar 2015)

markk said:


> for CO2 @ 30ppm
> - kH 1: pH = 6.0
> - kH 4: pH = 6.6
> Have I got that wrong?
> or do I need some fresh air



Not sure what youre doing. You are supposed to do from pH at equilibrium (which is whatever pH has a CO2 ppm of around 1.5) down to the pH at which you get 30 ppm CO2. This for each kh that you want.

I think what you are doing is comparing the pH for 30 ppm CO2 for each kH. This is not what I mean.
What I mean is the "jump" of pH for the same water (not at different khs)


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## markk (5 Mar 2015)

Jose said:


> I think what you are doing is comparing the pH for 30 ppm CO2 for each kH. This is not what I mean.



But that is exactly what you've referred to in the quoted thread - and that is what I was responding to.

For clarity, this is the text I'm referring to.



> here are his exact words from another one:
> 
> "Say you have 30ppm CO2 in a KH of 10 and a 30ppm CO2 in a KH of 1.
> 
> ...



The 1.0 pH difference is entirely coincidental for the two kH solutions he has chosen.

Anyway...

For additional clarity, yes - you are correct about the consistent drop in pH across different solutions (i.e. kH is notionally irrelevant). I should have made that clearer earlier. Both Tom and ceg4084 are correct as well - they're just presenting it differently.

For the purposes of what you're trying to achieve, I can't help but think you're over analysing it. As you've already concluded, there may be too many other factors in aquarium/tap water to allow you to accurately predict the correct CO2 ppm using just the pH. If you go down that route, you'll be getting it 'about right' - which is fine - but you seem to want more. 

The alternative is to remove the other variables/factors - which is essentially the beauty of the drop checker. 4kH solution and a pH indicator. It's not ideal; it takes a while to reach equilibrium with the tank water and you have to 'interpret' the colour of the solution. But again, it will be 'about right'. (You could get really fancy and stick your pH meter in the 4kH reference solution in the checker...)

Regards

Mark


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## Jose (5 Mar 2015)

Then why does Tom Barr recommend a 1 ph unit drop whatever your water is? Because this is true for most waters no matter what they have in it. 1 unit ph isnt a coincidental value. I recommend doing a search please.

Anyway hopefully someone will take the time to answer my question which is quite important since it makes a hell of a lot of difference.


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## Lusitanos67 (6 Mar 2015)

Very interesting


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## Sacha (7 Mar 2015)

Yes, people on this forum seem to be obsessed with a "1 point pH drop before lights on". It's just an arbitrary calculation that depends entirely on the individual tank, I don't even bother testing my pH any more.


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## Jose (7 Mar 2015)

Sacha said:


> Yes, people on this forum seem to be obsessed with a "1 point pH drop before lights on". It's just an arbitrary calculation that depends entirely on the individual tank, I don't even bother testing my pH any more.



Its not arbitrary. Go to thebarrreport.com and do a search.

.....My questions remains unanswered.


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## Sacha (8 Mar 2015)

Your question remains unanswered because you do not understand how the pH scale works. You seem to be denying the well-known fact that KH is a pH buffer. 

It's a logorithmic scale. 30ppm of Co2 in a tank of KH 1 might drop the pH by 1, but the same concentration of Co2 in a tank of KH 10 will only drop the pH by about 0.3 or so. 

So a "Full pH drop before lights on" in a tank with KH 15 will most likely kill all of your fish. 

Furthermore, the Co2 concentration at the beginning of the injection period is rarely zero. So I you don't know what your concentration is to start with, how on earth do you work out when you have 30PPM? 

Finally, there are *many* other factors aside from carbonic acid that affect pH.


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## Sacha (8 Mar 2015)

Jose said:


> I have done it. Its always around 1 unit pH. Its not coincidence. You arent reading the table properly then.



What are you even talking about? Don't you understand that KH buffers the pH? The higher the KH, the less your pH drop will be _with the same amount of carbonic acid dissolved in the water_. It's ok if you want to deny this and say it's a lie, you'll just be wrong


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## Jose (9 Mar 2015)

I wont go through the same things again with you Sacha. Co2 is not an acid in itself but it creates an acid when in solution, this is why its behaviour is different. Its has been tried and tested (the 1 ph drop for different kh waters). This being said I dont think your ways are even worth answering to. Im just interested in the answers but I can see most people prefer to stay in their  confort zone so....

Its not always a 1 pH change. It can vary a bit I suppose depending on the buffers in your water. But it definately doesnt vary as much as cegs example. Its normally around 1 unit of pH, and normally not less than that.

Id really like to hear what ceg has to say on this.


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## Sacha (9 Mar 2015)

Jose said:


> Id really like to hear what ceg has to say on this.



Me too, I'm looking forward to his reply.


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## Jose (9 Mar 2015)

http://www.barrreport.com/forum/barr-report/co2-enrichment/2507-co2-measuring-1-ph-difference-method.


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## markk (9 Mar 2015)

Jose

One last go from me Please don't bite!

Sacha hit the nail on the head - the 1.0 pH figure is arbitrary.

For most people with water within reasonable parameters, dropping the pH by *about* 1point will give you *about* 30ppm CO2 with relatively little risk.

Have a look at:-

http://www.plantedtank.net/forums/showpost.php?p=4677466&postcount=7

regards

Mark


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## Jose (9 Mar 2015)

Sacha said:


> Me too, I'm looking forward to his reply.


No problem with being wrong its the best way to learn.


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## Jose (9 Mar 2015)

markk said:


> Jose
> One last go from me Please don't bite!
> Sacha hit the nail on the head - the 1.0 pH figure is arbitrary.
> For most people with water within reasonable parameters, dropping the pH by about 1point will give you about 30ppm CO2 with relatively little risk.
> ...



Youre are proving my point Markk. I never said it had to be exactly 1 ph unit (If I did I apologise) but around it. Definately not the 0.2 or 0.4 that ceg suggests. Kh has a minuscule effect on that (ph drop needed) and this is what my question was.

I know what you mean with the link though. Its not exactly 1 unit all the time buts it varies around 1-1.4.

So in practical terms: You take tank 1 and let water rest in a glass. Measure its pH. Then add co2 in the tank until you get a 1 unit ph drop in the tank.
Then take tank 2 (different kh) and do exactly the same.
You should get pretty much the same CO2 ppm for both if youre doing exactly the same.
At least this is very true if you do the ph/kh table example. And the ph kh table isnt real life but its a way to compare dferent khs.

I dont want to argue about exact numbers just the idea (see my question) about different khs and same pH drop (aprox).


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## Jose (9 Mar 2015)

http://www.barrreport.com/forum/barr-report/co2-enrichment/3097-ph-drop-co2-chart
Its inacurate as a method yes but its not bad to get an idea of the pH drop you need. It shouldnt be 0.2 or 0.4. at all.

So the questions is. If you have really hard water (like me 18kh), then do you not need as high a pH drop really?
If this were true you should be able to back it up with the pH/kh table doing the example for the extremes (say 2kh and and 19 kh). It turns out that you need exactly the same pH drop(this value is different depending on what equilibrium level you choose but its the same for both khs)


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## Rahms (9 Mar 2015)

alkalinity (which is what KH measures) is the ability of a mixture to counter acidic change. Therefore two solutions with the same pH but different alkalinity will give different pH drops, given the addition of an equal amount of H+ ions (from an equal amount of CO2 forming carbonic acid I presume). Buffering.

The table indicates that Hobbyist A (0.2 pH drop person) has 18.9 ppm in his tapwater. This clearly isn't the case, as I mentioned in my _first post_.  So now you have two possibilities:


*It is impossible to have pH 7.2 tapwater with KH 10---> the table is correct and the water would have much higher pH*
*It is possible to have pH 7.2 tapwater with KH 10---> the table is wrong*

The problem with #2 is that you're then asking people to use the table to prove that the table is wrong.


All I've really decided is that I'm going to measure my pH with a drop checker lol


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## Andy Thurston (9 Mar 2015)

i measure mine with fish and adjust the timing with ph pen. my dc is about 2.5hours late


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## naughtymoose (9 Mar 2015)

Big Clown, please clarify WHICH fish you use to measure your pH, and how you calibrate them...


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## Sacha (9 Mar 2015)

And also please provide a chart with fish on the X-axis and Co2 on the Y-axis?


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## Rahms (9 Mar 2015)

presumably some sort of gasps-per-minute will be measured?


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## Andy Thurston (9 Mar 2015)

ottos get red gills first.
next glowline tetras loose their glow
then things start dying cherrys, rcs, then fish.
I'll try find the pics
the trick is make small adjustments when your around to see the symptoms of too much co2


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## Jose (9 Mar 2015)

Rahms, there is a 3rd option which is that the tap water simply has some co2 dissolved in it due to the changing preassure in the pipes, temperature etc.


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## Andy Thurston (9 Mar 2015)

the pics are here
http://www.ukaps.org/forum/threads/andys-60l-cube.31194/page-7#post-368533
I got the order wrong the glowline stop glowing and then ottos get red gills
the otto in first pic is just starting to get uncomfortable their belly should all be white I think I've got a better pic of that somewhere


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## Rahms (9 Mar 2015)

Jose said:


> Rahms, there is a 3rd option which is that the tap water simply has some co2 dissolved in it due to the changing preassure in the pipes, temperature etc.



19ppm out of the tap?

not bad!


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## Jose (9 Mar 2015)

Yeap its very possible. It can even go higher due to many reasons. This is one of the reasons for pearling after a water change.


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## Rahms (9 Mar 2015)

Jose said:


> Yeap its very possible. It can even go higher due to many reasons. This is one of the reasons for pearling after a water change.



in that case, you'd only expect pH to drop 0.2 to get to 30ppm!


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## naughtymoose (9 Mar 2015)

I can see that measuring with fish is going to cause a lot of discrepancies. I like little fish- Ember Tetras and so on; does this put me at a disadvantage when comparing my pH with someone who likes big fish, such as Clowns?


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## Andy Thurston (9 Mar 2015)

naughtymoose said:


> I can see that measuring with fish is going to cause a lot of discrepancies. I like little fish- Ember Tetras and so on; does this put me at a disadvantage when comparing my pH with someone who likes big fish, such as Clowns?


Yes but how do you know what is too much for any fish until you see. if your going to do it by accident you may as well learn as much as possible from it. different fish are affected differently so perhaps some people are at a disadvantage.
re. the clown loach tank.  its low tech. the 16 clowns provide more than enough co2/nutrients for few anubias in that tank. having clowns is a big disadvantage, give me tetras in a planted tank any day


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## Jose (10 Mar 2015)

Rahms said:


> in that case, you'd only expect pH to drop 0.2 to get to 30ppm!



Yes, the pH drop is meant to be from the equilibrium. Thats why cegs values probably arent from equilibrium with the atmosphere (my guess here).


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## Jose (13 Mar 2015)

Here is the final answer to my question.

http://www.barrreport.com/forum/bar...2511-how-much-co2-and-um-oh-yeah-how-much-co2

So, yes ph drop is independent of kh. 

That means cegs example is not meant to be taken as a kh comparisson. It can be missleading, which has been proven by all people who gave their opinion. People here seem to think that in hard water you dont need as high a ph drop for getting getting 30 ppm of co2. This is wrong.


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## Jay1 (13 Mar 2015)

Wow I've got a headache! 
Can we just have no atmosphere and 100% pure water with no KH or GH then review the results I can live with that 
DC, PH PEN, EI, Co2, H20 = Plants and fish Happy IF NOT I'll go to spec savers.
From what I can tell Clive tries to get to a ball park, like we all do. 
If you over analyze or over complicate things you sometimes create more problems than solve!
I look at my tank and just relax.

*Is this a thread to disprove Clive's simple analogy of typical scenarios, or is this actually going to help you achieve your goals? *
TBF to Clive he doesn't need to justify himself as I see his contribution to this site, way out weighs his rantings of the Matrix which I still disagree with him its an alright rip off film!


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## Sacha (14 Mar 2015)

Jose said:


> So, yes ph drop is independent of kh.
> 
> *WRONG*
> 
> ...



There's no point continuing this discussion because you seem to think that you have a better knowledge of chemistry than qualified, trained scientists do. Read the peer-reviewed paper in the post below. 

You can continue being wrong if you prefer, I can't be bothered to argue with you anymore.


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## Sacha (14 Mar 2015)

http://users.rowan.edu/~jahan/Jahan-Hands on an Aquarium/lecturelabs/interactionsphetc.pdf

Go to the section on the second page, entitled 'alkalinity, pH and Carbon Dioxide concentrations' 

*In water with moderate to high alkalinity (good buffering capacity) and similar hardness levels, pH is neutral or slightly basic (7.0 to 8.3) and does not fluctuate widely. Higher amounts of CO2 (i.e., carbonic acid) or other acids are required to lower pH because there is more base available to neutralize or buffer the acid. *

I'll repeat it in case you still don't understand. 

*Higher amounts of CO2 (i.e., carbonic acid) or other acids are required to lower pH because there is more base available to neutralize or buffer the acid.*

In case you had trouble reading that the first two times: 

*Higher amounts of CO2 (i.e., carbonic acid) or other acids are required to lower pH because there is more base available to neutralize or buffer the acid.*


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## Jose (14 Mar 2015)

Im not talking about the ammount of co2 sacha, im talking about the ph difference/drop. Please read the thread carefully. Also Tom Barr is quite a trustworthy source for me and many others.

By the way saying it three times doesnt make something true.

its a fact Sacha. Ph drop is independent of kh. Ive added enough info on here to proof this. Do you want me to add Tom Barrs actual words? I will. You are always giving a theoretical answer which is wrong.
Have you even tried this? All I know is that I can drop ph by 1.2 ph units in my tank with a kh of 18/19 without having any problem with fish. this would be impossible if I listen to your theory.

I think you are seing the carbonic equilibrium equation as a black and white thing. We are outside that equilibrium (we add co2)so it doesnt behave the way you think it does and its got constants in it which changes the magnitude of things. I hope you keep reading about this and get to the answer.

i will keep researching so that I can give you a better explanation. But the fat is the fact. After you know something by testing then you will explain it somehow. Yet if you have a theory without proof its just that a theory.


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## Jose (15 Mar 2015)

This is why I think ceg should have his say on this because many people just dont get it. I will try my best to get the fact out there. This is a very important question. Why doesnt he answer?

i just read your link Sacha. You dont even seem to understan my question. You dont differentiate ammount of co2 added and the ph drop generated by it. Its different things.

I dont care if people think  that I am overthinking this or if I want to discredit ceg (i dont hes helped me a lot). Im really just interested in the truth. This is a very important question. Why? A 1 to 1.2 ph drop is needed in high light tanks so as to suppress algae in some cases. If you think beczuse you have very hard water you need to drop the ph less then you arent in the right track which can lead to problems since there arent easy ways to measure co2.


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## Sacha (15 Mar 2015)

Ah, I see. You'd rather continue being wrong. That's fine by me, but this thread may as well be locked since you're not paying attention to a single thing anyone says here. 

This is my last comment here. My previous post contains all the information you need.


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## chandler (15 Mar 2015)

Jose, if you scroll down and read the comments under Clive's article, you see that he did some clarifications in one of the first posts. Hope that helps.


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## Jose (15 Mar 2015)

Thanks chandler. Ill have a look. Open to all new info.


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## Sacha (15 Mar 2015)

Jose said:


> Open to all new info.



LOL HE'S TROLLING US


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## Jose (15 Mar 2015)

Guys no need to get personal come on. Lets be civilyzed shall we. If two people dont agree lets just argument our believes. 

Chandler can you post a link I cant find what you mean.


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## Sacha (15 Mar 2015)

OK I did promise myself that I wouldn't waste my time replying here anymore but I just want to say one thing. 

This debate is not about 'agreeing' or personal 'beliefs'. It's about science, and well-attested chemical facts which for some obscure reason you seem to be denying. 

In more _basic _water, there is more _base _available which _neutralises _or _buffers_ any acid that you dissolve in the water (in our case Carbonic acid, a _weak acid). _This means that *the same amount of dissolved acid will create a smaller pH drop in more basic water. *

This is simple A-level chemistry. If you have some issue with it and want to propose a new theory, then by all means go ahead and do it. Let's see your research. Maybe one day you'll get your findings published in _Nature _or _New Scientist_. 

My point is: This is not a debate, or an argument. It's one person who doesn't understand the chemistry and so is trying to argue against well-attested facts of science.


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## Jose (15 Mar 2015)

Im not arguing about ammount of dissolved acid once again. Im talking about ph drop. Ph at eqilibrium-ph at X ppm of CO2.

here are Tom Barrs words

"PH drop is relative to an ambient non CO2 enriched tank, which should be about 2-3 ppm if things are going well.
If you view the pH/Kh/CO2 chart, for any KH value.the pH drop of 1.0- to 1.3 or thereabouts will = about 30-45 ppm.

That is independent of KH.

If the KH changes, or other acids are added to the system, the pH before/after start point will change, but the influence of pH due solely to CO2 will not.

Slow progressive adjustments and observations often are the best solution for CO2. Start with the pH/KH table, then adjust from there using the pH drop.
From there, everything is plant/fish observations.

SLOW progression, and lots of observation.
Never fast once you get up to the upper ranges"

Now this is me.
I know a higher kh has more ability to neutralize acids which is all you argue all the time. But this is not the question here. CO2 is not an acid but it creates an acid when dissolving into water. This reaction has a constant which can make things not as clear as you might think. Why the ph drop is independant of kh? I dont know, but its a fact proven by testing and observing.


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## Jay1 (15 Mar 2015)

*Can we just have no atmosphere and 100% pure water with no KH or GH then review the results I can live with that *

You just cant quantify a singular element and call it independant there are too many variables like Carbonic acids actually I think four different kinds of acids/alkalines to change PH, which is on gravel, filter media, water column, fish ornaments. Even you said it yourself co2 is in water before injection of co2. So you are open to the idea Sacha has made? 
Its an art *(Too many variables)* not an exact science, and maybe you are miss interpretting those reports because you are taking the language out of context or the use of the language is incorrect?   
AND I repeat myself again what are your goals and where are you intend to get too?


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## Yo-han (15 Mar 2015)

I hate stepping into heated discussions but I think I can explain why you people disagree. You both discussing similar but different topics. Jose is saying: I got 4 ppm of CO2 and want to go to 30 ppm of CO2, will my pH always drop 1 point, no matter what KH. So lets take a KH of 1, check the table from 4 to 30 ppm. About 0.9-1 point pH drop. Do the same at a KH of 20, still 0.9-1 point pH drop.

Sacha is saying, lets take a pH of 8 and a KH of 1, drop 1 pH point, do I get 30 ppm? No only 3 ppm CO2. Lets do the same at KH=20 and pH 8 and drop 1 point, you get >40 ppm CO2.

So if I'm reading this correct, it seems like both of your statements are right, but your discussing different topics.

So to get back to the first post, yes Jose, IN THEORY, your right. But to make it even more complicated, let's ask you a question: Is the only buffer in your tank carbonate (KH)? Is the only acid in your tank CO2? You think there are no buffers like phosphate, sulphate etc. in your tank? No acids like tannins, urine etc.? This means that unfortunately the KH/pH table tells you nothing, because that only applies to water without anything other than CO2 and carbonate. So in real life, the table tells you very little. A 1 point pH drop is quite accurate IME.


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## Jose (15 Mar 2015)

Hi yo-han. Thank you, thats not me against the world now. Anyway, to answer your question. My intend in the first place was to compare different khs, for this you have to rule out everything else like phosphate buffers etc, so that you can reach a conclusion solely on kh. In other words yes other buffers might have an effect on this but still the point is ph dropis independent of kh and the only way to test this is with only ro water and carbonates and co2 which turns out is the ph, kh table.


if you want to see the effect of kh on ph drop you have to remove all other variables from the equation.

It turns out that in our tanks it varies a bit but mainly depending on temperature, pressure, aeration etc. If you add an acid like a soil, then this will lower ph but also kh. The problem might come when you add a base/ a buffer i would think. But still its always around 1 to 1.2 independant of the water hardness.


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## Rahms (15 Mar 2015)

I've been thinking about this a lot and it's quite annoying  Even though you have increased buffering with higher KH, it seems you also have higher pH.  Since the pH scale is non-linear, you need less acid to drop the pH when its higher.  So although the amount of acid "buffered" (neutralised?) is greater, the effect on pH is also magnified.  The two effects act against eachother.... potentially levelling the curve out a bit.

But then, is the reason you have higher pH with higher KH simply because it removes (...buffers) some free H+ ions? Essentially the buffering effect has its main influence on the water before the CO2 addition, raising the pH.  Not really convinced either way. I'd stand by my first post though- the issue is whether you'd ever see 7.2pH water with the high KH (meaning 18.9ppm CO2 according to tables). And if so, the table is clearly wrong- but then why would it be right at 7.0?

Not sure any of this really matters, but it would be nice to know.


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## Jose (15 Mar 2015)

It matters because there isnt a reliable way for most people to measure kh. But you can measure ph with a cheap ph pen quite reliably.


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## Rahms (15 Mar 2015)

I think it was said a few pages back- you can rely on your drop checker to determine if you have enough CO2, because it is of known hardness.  And you can use your pH pen to see how steady your CO2 level is.

Once I actually get a pen I intend to have a look at this further. But again, most people don't bother with the tables or pH profiles, and still have excellent tanks


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## Jose (15 Mar 2015)

Yeap thats true. But it might save you some algae in the future. There are also many people who dial in co2 with a ph pen. I just dont like dropcheckers, because the mist co2 can just go into it and change the results.


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## Andy Thurston (15 Mar 2015)

I don't think it does, matter according to the tables I have 200ppm+ in my tank(1.2-1.3 ph drop) that's why I use livestock as a guide, too many variables in the tank mean all the numbers are useless. a 1 point drop is just a starting point then you usually adjust up(slowly) from there.
I use a ph pen to find the point where fish start gasping then use just less than that as an upper limit.
if you want to avoid algae stop getting hung up on numbers and dont have too much light easy!


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## Jose (15 Mar 2015)

Youre not using this method then  Big Clown. You dont have to measue kh. Just try a 1 ph drop and go from there. Its impossible to get 200 ppm co2 with the method im talking about here. You decide your co2 ppm and then check the ph drop that you need. Not the other way around.


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## Andy Thurston (15 Mar 2015)

your right I'm not using that method, been there done that, had algae, realized the numbers were funny and increased co2. never looked back
I use as much co2 as I can and couldn't tell you the real ppm in the tank just like you can't tell me, with any accuracy, that you have 30ppm in your tank. so why waste my time reducing my ph drop to 1 point
tom barr writes in his first sentence that the *recommended ranges* are wrong and vary from tank to tank
http://www.barrreport.com/forum/barr-report/co2-enrichment/11862-co2-ph-kh-table


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## Jose (15 Mar 2015)

Yes ive already said the same as you in this thread before. Its not accurate neither is any method we use for measuring co2. Still this is not the point.


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## Andy Thurston (15 Mar 2015)

so if none of our ways of measuring co2/ph/kh are accurate then this thread becomes as pointless trying to measure co2 because you cant prove/disprove any of it and probably the same reason Clive hasn't made a post


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## Jose (15 Mar 2015)

You could think so if yoou want. 

What you say makes the idea more important because the more methods we have the better, since they arent accurate.


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## oviparous (15 Mar 2015)

Yo-han said:


> but I think I can explain why you people disagree. You both discussing similar but different topics.
> 
> So if I'm reading this correct, it seems like both of your statements are right, but your discussing different topics.


+1

Sasha's theory is correct when you want to lower the pH by adding acid, THAT DESTROYS THE KH.
In that case, the higher the buffer the harder it is to get the pH down. So if you add the same amount of acid in 2 solutions, the one with the lower KH will have a bigger pH swing vs. the high KH.
Example:
If you go from KH=1 to KH=2 with CO2= 10mg/L, the pH  goes from 6,45 to 6,75. A difference of 0,3 pH.
If you go from KH=19 to KH=20 with CO2= 10mg/L, the pH  goes from 7,73 to 7,75. A difference of 0,02 pH.
So you can see there is a big difference.
Doubling/halving the KH, you always get a 0,3 difference in pH.

CO2 doesn't destroy the KH (actually it does, but only a tiny bit), so then the CO2 chart comes in to play.
And there you can see that Jose is 100% correct! If Jose was wrong, that would mean the CO2 chart is wrong. And i think that chart passed the test of time.
If we go from 10mg/L CO2 to 20mg/L with KH=2. The pH goes from 6,75 to 6,45. A difference of 0,3 pH.
If we go from 10mg/L CO2 to 20mg/L with KH=20. The pH goes from 7,75 to 7,45. A difference of 0,3 pH.
If we start and end with the same CO2 concentration, but a different KH, the pH difference is always the same!


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## Jose (15 Mar 2015)

Thats the thing oviparous. People think that co2 is an acid an therefore at higher khs the buffering capacity makes it harder for ph to go down with the same co2 ppm. Well this is wrong although its what youd expect by intuition.

So this has become a myth in this forum and this is why it would br helpfull if an expert made everyone realize the truth because obviously my words arent good enough for that.


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## chandler (15 Mar 2015)

Clive's words: 

Hi,
Thanks. Sorry to muddy the water. :? What I was trying to say was that the final pH value would be lower after adding 30ppm to a lower kH water. In reality if A and B sample waters started off at KH 10 and KH 6 and if both had the same starting CO2 level then sample B (the lower KH) would start off with a lower pH than sample A. After the addition of 30ppm the "delta", or, change in pH would be the same but the starting and the final pH values would be different. I should probably clean that up.

Me: though I do not completely get what the fuzz is all about i think this clarifies ceg's example.


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## Jose (15 Mar 2015)

Oh great Chandler, so that explains it all. Could post the link please?
See? He admits he should clean it up because its very missleading specially since its such a myth as Sacha has proven. He said I was trolling you all? This isnt really about me so no worries..


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## chandler (15 Mar 2015)

Just look under the drop checker tute... Not sure how to link to it


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## Jose (15 Mar 2015)

No worries then. 98% of people here dont know this truth, thats all. I thought since its a site based on quite good knowledge that it would be a good fact to stablish. 

About people who just cant argue science and who get personal if removed from their confort zone..... we can just forget about them all.


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## Jose (16 Mar 2015)

I dont want to throw more wood to the fire but this are cegs words from Sachas post:

http://www.ukaps.org/forum/threads/my-ph-profile.31565/page-4

"The rest of the advice goes like this:
"If you have a low KH then you need a much larger drop by lights on"
"If yuo have very high KH then you may not need a 1 unit drop. A 0.5 unit (or so) drop may suffice"

Few people in UK have low KH, so generally a 1 unit drop is the target.

If your fish are fine then you can improve the injection rate, but be there to monitor.

Cheers,"

So it seems to spread the myth even further.


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## roadmaster (16 Mar 2015)

I am reminded of the sounds of the locust's I hear while night fishing on the river/lakes  .
Although they have nothing of discernible importance to say far as I can tell,they none the less continue with their chatter as is their nature to do so.
I suspect they enjoy hearing the sound they make.


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## Jose (16 Mar 2015)

roadmaster said:


> I am reminded of the sounds of the locust's I hear while night fishing on the river/lakes .
> Although they have nothing of discernible importance to say far as I can tell,they none the less continue with their chatter as is their nature to do so.
> I suspect they enjoy hearing the sound they make.



Ignorance is up to each one to have for their own. Me, I like knowing. Once again its not about me.


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## Jose (16 Mar 2015)

Jose said:


> far as I can tell


exactly. If you dont get it, walk on. This is not for beginners and people who dont want to know the intricacies of the hobby.


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## roadmaster (16 Mar 2015)

Jose said:


> Ignorance is up to each one to have for their own. Me, I like knowing. Once again its not about me.



Well, I would not go so far as to call the insect's ignorant,just annoying.


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## Mortis (29 Mar 2015)

Jose both you and that guy who says you are 100% are going around in circles. First you were saying that a 1pH drop in any KH equals around 30ppm CO2 then that other chap says that with a lower KH 30ppm of CO2 will cause a larger drop in ph (the 1-1.5 you have mentioned) and he also says that with a higher KH with 30ppm CO2 you will get a smaller drop in pH of around 0.5.

You agreed with this statement because he said  you are 100% correct but it kind of contradicts yours.

Your tap water CO2 has no importance because it will only be a factor on the day of your water change so lets ignore it w.r.t the calculations

Ill just try to summarise this simply :

If you have a low KH and add 30ppm CO2 you will see a large drop in pH
If you have a high KH and add 30ppm CO2 you will see a smaller drop in pH

The key point here is that you are adding 30ppm of CO2 in both cases and reaching the CO2 levels that you need in your planted tank. you arent adding CO2 to lower the pH of your tank or to neutralize the KH carbonates. So no matter whether you get a small or large swing in pH you are still adding enough CO2 for your plants.

The KH and pH charts are only to make it convenient for you to figure out your CO2 levels in terms of ppm


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## Andy Thurston (29 Mar 2015)

Mortis said:


> The KH and pH charts are only to make it convenient for you to figure out your CO2 levels in terms of ppm


 and they cant do that with any accuracy according to those charts and my water report I'm pumping 200 ppm of co2 into my tank but they are a good starting point


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## Jose (29 Mar 2015)

All this has been discussed in this very thread already.


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## sciencefiction (11 Apr 2015)

When CO2 dissolves, being a weak acid, the amount of H+ released is enough to drop the Ph but not enough HCO3- are released to affect the Kh itself(you may need to inject a thousand more times of CO2 to actually affect the Kh).  That's why alkalinity doesn't matter when dissolving CO2 and also your fish aren't affected by the Ph drop as it' doesn't affect the KH. Well at least that's how I understand it.


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## GreenNeedle (11 Apr 2015)

The 1ph drop is a generalised statement relating to near neutral Ph with a supposed KH that relates to that Ph.  Aiming for a 1ph drop is a good starting point for most people.  To explain in more detail the poster may as well say nothing other than 'Here's a linky to a ph/KH chart'.

This is the reason we use drop checkers with an known 4KH solution within it.  We know it is not contaminated by anything else that would affect the result being that 30ppm will change the colour of the 4KH solution (with its bromo blue reagent) from blue to green.

You can do the same with the ph/KH charts BUT you then need to know the ph and KH of your water sample(s) and you are also allowing contaminants that are in the tank sample(s) to potentially affect the result.

So there is no contradiction really.  It is a generalised statement which will be close enough for most people and at worst a good starting point versus going into detail about the relationship between KH and PH.

At the end of the day (IMO which can be a bit sharp) is that if someone couldn't be bothered to (re)search themselves about the PH/KH relationship then a statement of 'Aim for a 1ph drop' is probably the best answer for them.


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