# high pH normal kH



## beaslbob (Oct 17, 2012)

I wonder what could possibly be determental to any fish if a tank with normal kh (4 degrees german hardness or so) but a very high pH like 8.4-8.8 api high range test kit. Assuming the pH is high due to plants sucking out and lowering the carbon dioxide.

Even though that would be conditions not found in nature for many fish, why would that be detrimental?


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## corina savin (Jul 11, 2012)

Unless your pH is 7.4 before lights and 8.4 when lights are out, you cannot assume that high pH is because of plants using CO2. Scratch that.


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## beaslbob (Oct 17, 2012)

corina savin said:


> Unless your pH is 7.4 before lights and 8.4 when lights are out, you cannot assume that high pH is because of plants using CO2. Scratch that.


HUH?

Oh how so?

pH rises from some lower value to some higher with the lights on.

before adding plants the pH was 7.6 (marine tank). after adding plants (macro algae) pH rose to and stayed at 8.4-8.8 just before lights out. the lowest pH with macros was still higher then the highest non macro ph (8.0 vrs 7.6)

Ph in FW test jars with a baby guppy with crushed oyster shells, crushed coral, bare bottom, play sand, and peat moss all have a pH of 8.4-8.8 with plants but 7.0-7.6 in darkness.

So like I said how so.

that would all seem to point to plant action.


my .02


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## Mikaila31 (Dec 18, 2008)

You would need to look at a lot more then pH and kH to figure that out. 

I doubt its CO2 tho with a kH of 4 your not gonna get anywhere near the concentration of CO2 in the water to throw pH that much without injecting it. The only way plants can affect pH is via CO2 and some carbonic acid uptake. 

Marine is a another thing that I don't touch.

I would question whatever you are testing pH with and how long you let those jars sit. Then GH levels and ect.


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## beaslbob (Oct 17, 2012)

Reference: http://www.tropicalfishkeeping.com/...cussion/high-ph-normal-kh-406762/#post4572242

Dr. Randy Holmes-Farley has posted several excellent articles on marine/reef tanks over the years and came up with the diy 2 part method for maintaining cal/alk/mag on reef tanks. That article has pH/kH wraped up in a nice package with the equations graphs etc. Although the article is aimed at the reef tank the pH,kH,CO2 are the same exact equations and apply equally well to FW tanks. I encourage everyone to research these ideas and post any differences you find.





Mikaila31 said:


> You would need to look at a lot more then pH and kH to figure that out.


Yep you need carbon dioxide.



reference article said:


> 3. CO2 + H2O à H2CO3
> 
> 4. H2CO3 ßà H+ + HCO3- ßà 2H+ + CO3--


So as co2 (equation 3) is lowered, less h2co3 is produced, and less h+ is produced raising the pH.

As the graph shows below lowering the co2 from plants raises the pH with no effect on kH.




> I doubt its CO2 tho with a kH of 4 your not gonna get anywhere near the concentration of CO2 in the water to throw pH that much without injecting it. The only way plants can affect pH is via CO2 and some carbonic acid uptake.


 
Correct. plants lower the co2 raising pH. In low co2 environments they can use carbonate ions directly for carbon which would tend to lower kH (and pH). IME the overriding effect is the lowering of co2 just as happens in lakes and lagoons FW and marine. Both have a nightly pH drop. 



> Marine is a another thing that I don't touch.
> 
> I would question whatever you are testing pH with and how long you let those jars sit. Then GH levels and ect.


You can simply get a dozen jars and duplicate the experiment. 6 lighted and 6 in darkness. various substrates, feeder guppies for bioload. plants in darkness experience the expected pH, kh, gh reactions. Lighted, planted jars all had pH rise to high levels after a month.

One marine tank rose from a pH of 7.6 to 8.0 in three days after adding macro algae. Then to 8.4-8.8 after about a month. And stayed at the level for years. KH needed to be dosed after awhile to maintain at 8 degrees.

Planted sand only tank had pH of 8.4-8.8 and kH rose to 20 degrees gH 35 degrees after a couple of years. Planted tanks with peat moss had pH of 8.4-8.8 after a month or two after an initial 7.0 or less pH. KH remained a 4 degrees and gH at 9 degrees for over two years.


still just my .02


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## corina savin (Jul 11, 2012)

Your reference article is wrong. You posted it in another thread and I did not comment. I cannot trust the conclusion if the writer is sloppy with his original statement:
CO2 + H20 leading to carbonic acid is a reversible reaction, should be written as <---->, just like the other two underneath. And this is very important.
Equation (4), the last term: carbonate, should be written (CO3)2-, not CO3-.
Not big deal, I know, but its enough for me to dismiss the rest.


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## Mikaila31 (Dec 18, 2008)

That thinking of the relationship between pH/kH/CO2 is flawed. There has always been charts relating these since before I started this hobby. These are only accurate in a stand alone system, where you have nothing else interfering, not in an aquarium. CO2 and HCO3 are not the only acidic compounds produced in an aquarium. Thats why its not recommend to use the charts, they are much more accurate and safer means to measure CO2 that work off the same principle but without the uncertainty.

My water also has a kH of around 4. I run pressurized CO2 injection and I see maybe the same drop over standing tap water. Down to 6.5 from high about 8. I however am running 30ppm of CO2 which is no where near the amount of CO2 you will get out of the atmosphere. Going by what you believe is happening all my fish would be dead. Also CO2 turns off for the night but my pH never fluxes that much on a daily basis.

If you are getting the same numbers across the board with separate containers of crushed coral, peat moss, driftwood something is wrong with your method. 

Corina already mentioned the link is wrong amongst other things.


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## beaslbob (Oct 17, 2012)

corina savin said:


> Your reference article is wrong. You posted it in another thread and I did not comment. I cannot trust the conclusion if the writer is sloppy with his original statement:
> CO2 + H20 leading to carbonic acid is a reversible reaction, should be written as <---->, just like the other two underneath. And this is very important.


fine. so lets write it as:

_3. CO2 + H2O <-->H2CO3
_

_and while we're at it:_
_
4. H2CO3 <=-->H+ + HCO3- <-->2H+ + CO3--_

_Now how does that point change in any way the fact that lower CO2 lowers H2CO3 and therefore with 4 raises pH?_



> Read more: http://www.tropicalfishkeeping.com/newreply.php?do=newreply&p=4573402#ixzz345c8a4qJ
> 
> 
> 
> ...


 [/quote]

same equation show up in Corrected pH-KH-CO2

care to provide your reference?

As I review:

4. H2CO3 <--->H+ + HCO3- <--->2H+ + CO3--

There are 2 hydrogen 1 carbon and 3 oxygens in all the equations and the positive and negative charges balance also.

I'm also confused as to what you mean by (CO3)2-. It that a co3 with two -'s or do you mean 2(co3)--? 

Finally I hope you're not saying that adding carbon dioxide does anything but lower the PH. Plus some affect on kH also. After all adding CO2 is the basis of calcium reactors plus the lowering of pH is used to adjust co2 systems in FW.


So back to my original point. Plant action lowers CO2. Resulting in a high pH. And how can that possibly be bad for any fish? Even if it not realized in nature where the fish are from?


my .02


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## beaslbob (Oct 17, 2012)

Mikaila31 said:


> That thinking of the relationship between pH/kH/CO2 is flawed. There has always been charts relating these since before I started this hobby. These are only accurate in a stand alone system, where you have nothing else interfering, not in an aquarium. CO2 and HCO3 are not the only acidic compounds produced in an aquarium. Thats why its not recommend to use the charts, they are much more accurate and safer means to measure CO2 that work off the same principle but without the uncertainty.
> 
> My water also has a kH of around 4. I run pressurized CO2 injection and I see maybe the same drop over standing tap water. Down to 6.5 from high about 8. I however am running 30ppm of CO2 which is no where near the amount of CO2 you will get out of the atmosphere. Going by what you believe is happening all my fish would be dead. Also CO2 turns off for the night but my pH never fluxes that much on a daily basis.
> 
> ...


While you're free to disagree, scientifically running the same experiment is the only way to validate or disprove the results. But that does require work.


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## Mikaila31 (Dec 18, 2008)

Yes plants can lower pH under certain circumstances, thats a proven fact, just not what I think is going on here. Its not an absolute that plants can change pH and not something I would rely on to lower pH. You need high demand for starters and low to moderate buffering. 

Lowering CO2 will pull the rest of the carbonate equilibrium with it to varying degrees but that is again assuming its a closed system and no carbonates are being added which isn't always the case in an aquarium.

pH meters for CO2 systems again are not widely used because many of them are subject to the same error. Drop checkers are currently the standard means of testing CO2 since it involves purified water with 4dKH that is held in a chamber seperate from the aquarium water. You judge CO2 off the indicator change in this water since it cannot be thrown off by anything other then gas exchange. The water in the drop checker follows the basic CO2/pH/kH chart since nothing else interferes. On the other hand if I dumped a bunch of driftwood into my tank I know pH is gonna drop to the same or lower levels then when I inject CO2. Any pH meter is going to see that and assume its from CO2 and stop injecting, likewise if you add something that leeches basically the you risk over injecting. 



> While you're free to disagree, scientifically running the same experiment is the only way to validate or disprove the results. But that does require work.


Which is basically my job you are describing lol. You have not shared your experiment so it can't really be replicated. Not saying I will repeat it but not saying I won't either, not during summer anyways. The first step in that is knowing in detail what you did, what you used, volumes, species, duration, testing method, brands, your results, duplicates, ect. Prior to any of that no one can really replicate anything. Typically bob getting enough info out of you to figure out anything is the challenge;-). Leave out anything SW that is no use to this section or me.


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## beaslbob (Oct 17, 2012)

Adding plants raises the pH not lowers. Which is the effect I have been discusstion.

the experiment was a dozen quart jars half in darkness half with plants with lit for 8 hours. tap water kh4 gh9. no water changes. water level marked and maintained. each set had the same various substrates, bare bottom, crushed oyster shells, sand, sand with peatmoss, crushed coral. After a week feeder guppies were added to the planted jars and no food added for a week. then I fed very small flake per day was fed. 

the unlit jars showed various pH values ranging from under 7 to around 8. The planted jars showed similiar initial pH values but pH started to rise in the lower ph jars. After 30 days ph in all the planted jars was above 8. After 6 months pH in all the planted jars was above 8.4 . api high range test kit. KH and gh in the peat moss jars remained at 4 and 9 but slowly rose in the non peat moss jars.

Should be enough for you to disprove. But it does require work

my .02


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## corina savin (Jul 11, 2012)

"Adding plants raises the pH not lowers". 
Good. Lets focus on this one. This statement is only partly true. To make it entirely true, it should read: "plants raise the pH during photosynthesis, until they consume all available CO2". In a not so heavy planted pond, that's about 4 hours, every morning. For the rest of the day, even if light (sun) continue and CO2 levels start to build up again, plants do not raise pH. Photosynthesis cease quickly once CO2 is zero. During night, as plants release some (but not all) of the CO2 "inhaled" during the day, during that time, plants actually lower the pH (not raise). Before the sun is up (or lights are on) next day, hopefully, CO2 level has recovered, reaching the same level or more than previous day, and the process repeats itself, day after day, night after night.
Plants have no ability to raise the pH more than it was lowered in 24 hour cycle. Also, plants cannot raise pH and hold it there.
That's why I said, at the beginning, that you cannot assume that high pH is because of plants, without mentioning at what time was that measured and how low was before that.


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## beaslbob (Oct 17, 2012)

corina savin said:


> "Adding plants raises the pH not lowers".
> Good. Lets focus on this one. This statement is only partly true. To make it entirely true, it should read: "plants raise the pH during photosynthesis, until they consume all available CO2". In a not so heavy planted pond, that's about 4 hours, every morning. For the rest of the day, even if light (sun) continue and CO2 levels start to build up again, plants do not raise pH. Photosynthesis cease quickly once CO2 is zero. During night, as plants release some (but not all) of the CO2 "inhaled" during the day, during that time, plants actually lower the pH (not raise). Before the sun is up (or lights are on) next day, hopefully, CO2 level has recovered, reaching the same level or more than previous day, and the process repeats itself, day after day, night after night.
> Plants have no ability to raise the pH more than it was lowered in 24 hour cycle. Also, plants cannot raise pH and hold it there.
> That's why I said, at the beginning, that you cannot assume that high pH is because of plants, without mentioning at what time was that measured and how low was before that.


 
Yeppers plants consume co2 and produce oxygen lights on and reverse lights off. 

Now my point is that the lowest (at night pH) in a planted environment is still much higher then in a non planted environment. As my tests with the jars showed. And my 55g with a pH (marine) of 7.6 just before lights out that rose to 8.4-8.8 (api high range test kit) after adding marco algaes. With low kh it dropped to 7.9 just before lights on. With kH buffered up to 8 degrees the pH dropped to 8.2 or so.


Yep you're right. But the plants have resulted in a higher pH then without.

So the effect of the plants was to make the tank a net consumer of co2 and producer of oxygen each 24 hour period.

Hence, even with the nightly pH drop and even though at the steady state the co2 does recover at night, the co2 levels with plants are much lower then without. And pH rises reflecting that.


Again all this happened with the only difference being the addition of plants. 

my .02


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