# pH Up and measuring CO2 levels.



## asincero (Mar 25, 2006)

Several months ago ... around January I believe ... I tried using pH Up to raise the pH of my tank. I haven't used any of that stuff since. I'm now interested in putting in a pressurized CO2 injection system, and I would like to be able to measure how much CO2 is being put into the tank. I read that products like pH Up can mess up the calculations used to measure CO2 levels in the tank. Would the pH Up still affect CO2 calculations now even though it has been several months and surely the water in the tank now is completely different from the water that was in the tank then? Does the stuff stick to the rocks or something?


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## Minsc (May 7, 2006)

PH up is just baking soda, which raises your KH.
It won't mess up your CO2 calculations.

All the pH down type products will throw you off, however.


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## asincero (Mar 25, 2006)

Minsc said:


> PH up is just baking soda, which raises your KH.
> It won't mess up your CO2 calculations.
> 
> All the pH down type products will throw you off, however.


According to this article:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

ph-UP is a phosphate buffer, and therefore would screw up CO2 calculations.


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## asincero (Mar 25, 2006)

asincero said:


> According to this article:
> 
> http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
> 
> ph-UP is a phosphate buffer, and therefore would screw up CO2 calculations.


However, I just went to Aquarium Pharmaceuticals web site, and they said ph Up contains no phosphates. In fact, the "Chemwatch Material Safety Data Sheet" PDF for ph-UP confirms that it's nothing but sodium carbonate. So I guess that article must have been mistaken!


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## asincero (Mar 25, 2006)

I failed to mention earlier that I also used Proper Ph 7.0 a few times too. Again, this was several months ago though. Could this product still affect CO2 calculations now even though it's been several water changes later? Aquarium Pharm's web site does not indicate whether or not this product has any phosphates in it or not. Since it should have the ability to lower the pH of water, it's clearly not simple baking soda. The MSDS sheet lists several of the ingredients as "Trade Secret" :suspiciou.


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## scitz (Mar 16, 2004)

I was under the impression that the pH UP powder is nothing but sodium bicarbonate, aka baking soda. However the pH UP liquid was a sodium hydroxide (NaOH, my chem names might be off) solution, or at least contained NaOH. Sodium bicarbonate would make too weak a solution for the "1-2 drops per gallon" type dosing. I hazily remember a warning on the back of a bottle we had floating around the store specifically mentioning NaOH.

pH Down is usually a phosphoric acid solution, or a powder that creates phosphoric acid in water. Most Phosphate-free' pH decreasers are based on Sulphuric acid instead.

The proper pH, Bullseye, and seachem line of pH *buffers* are a chemical cocktail of all sorts of goodies. The first 2 being notorious for not working unless added to fairly neutral pH water with low KH and GH.

Whats the point of providing at MSDS sheet if half your ingredients are "Top Secret"? pH is a _fairly_ easy to understand and manipulate parameter for your average BS in chemistry student. Plus anyone serious about ripping off these companies can have the sample analyzed and get a report on exactly whats in it, and what the concentrations are. The only real losers are consumers.

Sorry to thread-jack.

If you do a 100% water change, or several 50% wc's, you will have diluted down any residual proper pH to the point it wouldn't measurably affect using the pH-KH co2 charts.


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## asincero (Mar 25, 2006)

I checked my KH and pH and plugged those values into the CO2 calculator at:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

And it came out to 7.536 ppm of CO2. My KH is 10 and my pH is 7.6. The reason why my KH is so high is because I add baking soda to the water due to the fact that the water out of tap is so low in KH. According to that article, if your CO2 is over 5 and you're not injecting CO2, then something is in the water (such as phosphates) that's screwing up the calculations. Though 7.536 is not very far off 5, it still is over 5 and according to the article I shouldn't trust this result. Or can I?

It doesn't seem very likely at all that the Proper pH I put in the tank 6 months ago would be having an effect now. Especially since I do weekly 50% water changes and having just did one 2 days ago. I think I read that they sometimes put phosphates in the drinking water. Perhaps my city is doing that?

I also dose daily with Excel (I overdose in an effort to control an algae issue I've been having ... I use two caps instead of just one), and with Excel Iron. Could this be effecting the calculations?

How else can I measure the CO2 in my water? I'd really like to know how much CO2 I'm putting in when I install the pressurized CO2 unit. I don't feel good about just "winging it".


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## scitz (Mar 16, 2004)

test the water coming right out of your tap. Use that as a baseline. It could also be that you really do have a CO2 level around 7ppm. 

Note, let tap water sit for a hour or so to allow it to outgas. Since the water supply is pressurized, it contains more gas than it will if you let it sit for a while. Thats why your tank gets all 'fizzy' right after a large water change 
Also filling a clean soda bottle and shaking the living...out of it will help to outgas faster. It could also be your tests are off. With a KH that high, a pH error of only .2 either way can nearly double/half the calculated amount of CO2.

The KH of my tap ranges from 8-15 and I use cheap, easy to find pH tests so my calculated amount of CO2 varies wildly. I add enough CO2 that the plants happily pearl away and the fish don't look stressed first thing in the morning (co2 runs all night, DIY). When the plants don't pearl as vigorously, or start later and later in the day, I'll refresh my CO2 mix.

Unless you spend the time and money to get good test kits, and properly calibrate them using a solution of 100% known concentrations, you are always going to be 'winging it' I am afraid.


edit: A little note about precision taught in high school chemistry, your measurements can only be as precise as your lowest precision measurement. Meaning, if you have a test kit that gives pH to the closest .2, and KH to the nearest whole number 1,2,3,4,etc, you can't get a CO2 level out to the thousandths place .001. Plus when you factor all the "wiggle room" in comparing a test tube to a color chart when reading pH values, expect even more inaccuracy in those CO2 calculations. Such things are meant to give a rough estimation anyhow.


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## Bert H (Mar 2, 2004)

You say your water is very soft - how soft? A kh of 3 and above you're ok with. Raising it to 10, is rather high. Why not just raise it to 4?

After all these months of doing 50% weekly water changes, I wouldn't worry about the pH up you added. If it is indeed baking soda, there's nothing to worry about.

There are factors which will influence and throw off the kh/pH/CO2 relationship. But when starting out, I wouldn't worry about them. Take a sample of your tank water (not the tap), and let it sit out 24 hours. Measure the pH. Then aim for 1.0pH unit lower than that from your CO2 additions. That typically yields in the 30ppm range. Always keep an eye on your fish for signs of stress, and back off if you see it. If you find your fish are ok, and you need to go higher, slowly increase the CO2, again keeping a close eye on your fish. When you set up your pressurized system, try starting out with around 1 bubble every couple of seconds and adjust from there. The beauty of pressurized is that once you set it, you can pretty much forget it, unless your water parameters change.

The one thing here, is that you do need to have an accurate way to measure the pH. If your color kits are hard for you to decipher, try to find a kit which gives you colors which are easier to differentiate. Best bet, if you're going to be in the hobby seriously and can afford it, buy a pH meter something like this one.

Remember that you can ask your water company for a report on your water which will tell you its composition.

HTH.


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