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Question for ceg4048

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.
 
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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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?
 
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.
 
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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I've been thinking about this a lot and it's quite annoying :p 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.
 
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.
 
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
 
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.
 
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!
 
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.
 
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
 
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.
 
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.
 
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.
Click to expand...
+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!
 
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.
 
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.
 
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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