Can't figure out why ph is low

Boomer

Reef Sanctuary's Mr. Wizard
Prow

"sensitive to CO2 and pCO2 changes" dose not mean it changes those levels, nor does potentiate the effects. i dont know why you keep thinking i am saying alk changes CO2 levels. sensitive, as in not as drastic of ph swings, or in your words "the rate of pH drop, measured in time, from a Low Alk vs.

You are not going to see that in a tank unless the Alk is incurable low you. If a tank is 1.5 meq/ l, which is low, vs. a 4.5 meq/ l you are not going to see any measurable impact. I put that rate of drop in there to let you know, yes it is there, does happen but it is really trivial. You are drawing the conclusion that if the Alk is a little low the drop will be very noticeable and if you raise the Alk it will go away. You have taken that sensitivity thing and have greatly exaggerated its effect. It is like me filling up a 500 ml beaker with water and you look at it and say "Hey is it .5 ml to low, that will screw up your test"

You, I will assume, have read Randy's stuff, so point out a spot where he agrees with you. I actually got this rate of drop from him in a PM discussion IIRC. As I asked him can a high Alk do anything for pH drops as a pure function of CO2. See it any where in his articles ? If it was a big deal it would be there if nothing else as a warning. Show me where he says if your Alk is low and there is a CO2 issue you will see the pH drop much quicker, which is what your post implies. If you can I will shut-up :) Go back and read your posts, that was one of your theories.

Now let me throw this in there for that rate drop. If you have a pH of 7.9 and a Alk of 1 meq / l vs. a pH of 7.9 and a Alk of 3 meq/ l do you know that there is allot more CO2 in the water at that higher Alk ? So that so called faster rate of drop is almost canceled out with less CO2. On another post I posted a calculator for you to play with I had made for me. Did you not play with it ? It clearly shows that at the same pH an Alk of 2 meq /l has less CO2 in the water than a Alk of 3 meq / l. The amount of CO2 in water is dictated by the pH, Alk, temp and Salinity. And the same goes for Alk, if you know the Salinity, temp, pH and CO2 you can calculate it There are even massive programs on it used by chemical oceanographers.
 

Boomer

Reef Sanctuary's Mr. Wizard
Barb

Boomer, my system is an upstairs/downstairs system, with the sump and refugium in the basement... skimmer in the sump down there.... so could CO2 in the basement ALSO be a factor? Upstairs I've had the windows open because it's been so nice here. But downstairs... hmmm.

This has been brought up before and many times. That since CO2 is heaver than air, it will sink to a low spot and drop the tank pH. In almost any house, even with poor circulation, this is not a factor ir issue

As far as the rest of your post you are doing fine and there is nothing wrong with that pH or its swing.
 

SeaLover

Member
Boomer I will re test all my stuff right now and post it. You would def come in handy for my up coming chem class. meq? what does this stand for? Something from the metric system?
 

BarbMazz

Well-Known Member
Barb

Boomer, my system is an upstairs/downstairs system, with the sump and refugium in the basement... skimmer in the sump down there.... so could CO2 in the basement ALSO be a factor? Upstairs I've had the windows open because it's been so nice here. But downstairs... hmmm.

This has been brought up before and many times. That since CO2 is heaver than air, it will sink to a low spot and drop the tank pH. In almost any house, even with poor circulation, this is not a factor ir issue

As far as the rest of your post you are doing fine and there is nothing wrong with that pH or its swing.

So, I don't need to worry! Or do anything really different? Well, I definitely will stop overfeeding, though. lol

Thank you, again! :wave:
 

Boomer

Reef Sanctuary's Mr. Wizard
Barb

Well, no accept for that over feeding :)


Sealover

meq? what does this stand for

Are you sure you want to go there :) It stands for milliequivalents/ liter. Many beginning chem classes do not even discuss this unit of measurement that deals with the charged molar rate of an ion. The molar value of an ion has a milliequivalents value that is equal to its molar value multiplied by its charge. So if Ca++ had a molar value of 1 millimole, the meq/ l = 2 meq / l. As Ca++ has a charged of 2 and 2 x 1 = 2.0. If we now take something like Na+ then millimole = milliequivalents, as 1 /1 = 1. In short when ions are reacting they need to have the same milliequivalents value. That means that if our Ca++ was to react with Na+ we would need 1/2 has much Ca++ or twice as much Na+. As in, 1 millimole of Ca++ and 2 millimole of Na+. As, 1 millimole Ca++ = 2 milliequivalents and 2 millimole of Na+, 1 +1 = 2 milliequivalents Na+. And 2 - 2 = 0, thus it is balanced.

Now
Calcium=350
Alk=7.31


and before

75 Gallon Reef (Established 5 years old)
Salinity 1.026 (Refractometer)
DKH-8
P.H-8.1
Calcium-450 ppm
Magnesium-1400


Well, that pretty much tells the story. That use of buffers is pulling the Alk and Ca++ out of the water as a precip. Note how far the Ca++ has dropped and Alk. The Alk seems not to have drooped that much but really has as you keep adding buffers. This is a method some use to lower Ca++ when it is to high. although I don't like the idea. It is not that bad if one uses this method for that fix if they know what they are doing.. However, your method was not for that purpose and ended up that way and just made it worse.

In this discussion it was brought out that one of the problems may be an imbalance and this for most of us is what is going on in your tank, now that we can see those new parameters. Such issues as this can be hard to fix by adding things. It is best to do what 99 % of us would do when this happens. Multi water changes and I don't mean 10 %. I mean 25 % every other day or every day for a total of 4 WC and don't add anything to the tank or the fresh salt mix either.

In short, you tank was fine and you broke it by trying to get some parameter more to your liking when it was in accepted range. This is one of the biggest probes with many reefers. If you are within the accepted range leave the flippin' tank alone. It just amazes me, that if someone's pH is 8.2 for some nonsense reason they have to have it at 8.3 and the same goes for Alk and Ca++.

That bad thing on pH is kinda like a well kept secret to keep people away from the real pH of seawater in this hobby. When you see posted or read in most books the pH of seawater is 8.15 - 8.3. That is not the real pH of seawater. It is really 8.00 -8.15, as meter and many test kits are affected buy what is called the "Salt Effect Error'". Meaning, salt skews the pH reading making it read lower or higher than it is. In meters they read .15 pH to high. This is also why you see complaints from some as to why the pH meter reads 8.3 and test kit x, y or z is not the same or may be the same. Different test kits skew less or more and some not at all. No !!! that does not mean lets let it get that low in reef tanks for the same reason we like the Alk a little higher. We like a little "buffer" effect, as it is not the ocean or a reef. The only time you see the real pH of seawater is in advanced chemical oceanographer books. It is called pHsws and we use pHnbs. Reason, it would cost an arm and leg to get a pHsws solution to calibrated a probe. Kits that are more or less a function of pHsws and are not skewed are Krodon and Instant Ocean/ SeaTest/Aqaurium Systems test kits. The kit has to use metacresol prurple as a pH indicator. When chemcial oceanograhers do pH titrations with indicators in the lab ( no they don't use those kits) this is all that they use and is very accurate.


Reef Aquarium Water Parameters by Randy Holmes-Farley - Reefkeeping.com
 

Frankie

Well-Known Member
RS STAFF
This is one of the biggest probes with many reefers. If you are within the accepted range leave the flippin' tank alone.
Took me forever to finally get this. I am glad you posted this Boomer. I just replied in another thread here about someone saying Ca++ @ 400 was to low for there taste and the member should raise it. :dunno:
I also figured out that I am not a scientist and I do not need to over think my aquarium. My corals look good, my fish are swimming. I am happy :) My biggest reason why my corals look so well is because I do regular weekly water changes with a good salt.
(aside from stripping my water with zeolites, over skimming and dosing the crap out of my system with probiotics :D )
 

prow

Well-Known Member
Show me where he says if your Alk is low and there is a CO2 issue you will see the pH drop much quicker, which is what your post implies. If you can I will shut-up :)
why you got to go and make me look things up, lol.. ok you you asked for it.
A buffer is something that helps minimize pH changes in the presence of added acid or base. No buffer can completely stop the pH from changing when acid or base is added. The change in pH, however, is made smaller when an appropriate buffer is used.

The most important fact to reefkeepers is that the buffering due to bicarbonate and carbonate, at a given pH, is directly related to the carbonate alkalinity. If you double the alkalinity, you double b, and hence have twice as much buffering due to the carbonate and bicarbonate system. In normal seawater, the carbonate/bicarbonate system provides a substantial portion of the total buffering (which is quantified below). Consequently, marine aquaria with higher alkalinity tend to have greater buffering against pH swings
these from here Chemistry and the Aquarium

now shut up about it.........:D
 

Boomer

Reef Sanctuary's Mr. Wizard
Prow you just never want to listen do you when you are in error :) You are digging post holes here buddy. Where in the quote is the word CO2. Where does it say that a low alk is affect more so or less so by CO2 in dropping or raising the pH. Where does its say that a buffer buffers out CO2 ? Randy will tell you flat out that CO2 is a different issue. He says so in the article you posted. How many times do I have to say that Alk is not effect by CO2 and CO2 is not effected by Alk. And how many times do I have to say that no mater what the Alk if CO2 enters the system there will be a drop in pH no matter what the Alk is. CO2 is NOT part of the buffer system and CO2 is NOT part of Alk. In short, you don't understand pH, CO2 and Alk relationships. I guess Randy and I are all wrong then on the chem forum on our 100's of posts like mine here all saying the same thing. Go have a look.

They only one that need to shut-up is yourself :)

You post something without reading the whole article. How'd did you miss this ;)


The fundamental explanation is that the tank is deficient in CO2. In effect, the tank has an internal pCO2 that is more like that for the preindustrial air with 273 ppm CO2 (Figure 2). In this case, driving more CO2 from "normal air" into the water ****would lower the pH to about 8.2-8.3 while maintaining the same alkalinity.****

Where does he say that an alkalinity of any value is going to stop this from happening.

Likewise, tanks that use calcium carbonate/carbon dioxide reactors often have a pH of 8.0 with an alkalinity of 3 meq/L (or more). Again, that set of values falls off of the theoretical curve shown in Figure 2. In this case, the tank has an artificially high internal pCO2 of more than twice "normal air". Driving more CO2 from the tank into "normal air" ****would raise the pH to about 8.2-8.3 while maintaining the same alkalinity.***


And what is he saying ? What I just said AGAIN that no mater what the Alk if CO2 enters the system there will be a drop in pH no matter what the Alk is.


You high-lited

The change in pH, however, is made smaller when an appropriate buffer is used.

Of course it does the more buffer the higher the pH and Alk, depending on the buffer used. That is why one adds BS as it has much less impact on pH than say BBS does. So what's new. You should know that if you add BS and watch the pH upon addition what happens to the pH even though the Alk has gone up Prow. The pH drops doesn't it ? But what, the Alk is now even higher and did not stop the CO2 addition from the buffer and stop the pH from falling now did it ;) It still dropped. Do you see where I'm going here ?

Consequently, marine aquaria with higher alkalinity tend to have greater buffering against pH swings

Yup unless there is an increase in CO2 then it drops no mater what the Alk is for the 100th time :) Go back and re-read Randy's quote.

A buffer is something that helps minimize pH changes in the presence of added acid or base

See those words, "Base and Acid". CO2 is a gas and has no charge correct ? So, it is not a base or acid correct ? Unless it gets converted. What happens, in short, is in the reactions we could say, that the CO2 does drop the Alk. However, when the reaction is all complete there is a net gain in short of 1 H+ and 1 OH- and the two cancle themselves out and the Alk remains thte same.

Did you know and most that do know me know, that my favorite subject in this hobby is the CO2/Carbonate System along with GAC? And you want to argue about it. :)

The pH of water is dictated by the amount % of CO2, HCO3- and CO3-. If the pH drops from 8.3 to 8.2 there will be more CO2, more HCO3- and less CO3--. If we raise the pH to 8.4 there will less CO2 and more HCO3- and CO3--. Here is a graph to show this, it is called a pC-pH diagram.

13463d1216056226-im-confused-kalk-dosing-through-ato-figure1.jpg
 
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BarbMazz

Well-Known Member
Well, yeah, Boomer, I WILL stop overfeeding starting right now. :D

I have to say I love it when you guys argue chemistry. Each time I read these back-and-forths I absorb a little bit more. So thanks!
 

SeaLover

Member
Great advice Boomer. I get it. Will start water changes tomorrow. I had to read all that twice! lol Water change city!
 

Boomer

Reef Sanctuary's Mr. Wizard
Ok :)

Well, I'm done with this back and fourth Barb. Prow can come to our chem forum on RC and ask Randy himself and then come back here and post our replies ;)
 

prow

Well-Known Member
boomer you jump to conclusion about my posts. first i ask what his alk was. you assumed i was thinking alk controled ph with your following post. then i said alk effects the impact CO2 has, you jumped and assumed i was saying alk controls CO2 levels. the you went on to suggest i was saying alk determines CO2's effect on ph.(i see where you got that with my use of your words) the rest not sure how you jump to those conclusions even though i pointed out i did not say those things.

to put it simple;
tanks with lower alk and high pCO2 levels have a lower saturation state comapred to tanks with high alk and the same pCO2 level, in regaurds to aragonite. SeaLover's last ph reading was 7.8 (i am sure its lower during the night). with that ph a higher alk will increase the pCO2 saturation state. thus alk dose effect the impact CO2 has. i never said alk changed pCO2 levels or ph in regaurds to CO2. i said alk effects the impact CO2/pCO2 levels have period, you jumped on the idea that i meant alk effects changes in CO2. you assumed i meant Alk effects pCO2 changes. but i said alk effects the impact of pCO2 changes. do you see what i am taking about?
 

SeaLover

Member
First of all I am a her. lol
Second I tested the water from my lfs that I use for water changes and so far I can tell you the calcium is at 300 ppm. This is the ro/di water i buy in a 5 gallon bucket. 300....hmmm what could this mean. They arent mixing their salt right?
 

SeaLover

Member
I just tetsed the ph of the change water and it was 7.6! Now I know where the prob is. Its not in my house. Its in their water. I just added some buffer and brought it up to 8.0. We are aerating the change water too.
 

BarbMazz

Well-Known Member
Oh! Well, I meant Boomer and prow going at it over chemistry.

You could ask your LFS what mix they're using and what they think they're mixing it at. Times are tough? Maybe they're shorting on the mix to save some pennies?
 
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