Ph as a surrogate for dKH
- Thread starter yraveh
- Start date
Chris Lakies
Active member
To expound on this though... some people like me will put a limit on dosing limewater, such as if the PH climbs to above a certain level then the top off pump shuts down etc.
tinfoilsoldier
New member
yraveh, pH and alkalinity are related, but are not interchangeable.
pH is potential of hydrogen, or, is the water acidic or basic.
Alkalinity is additional info about how much acid/base it will take to get the pH to change.
If you have a low alkalinity, like putting a teaspoon of baking soda in a gallon of pure water, it will raise the pH slightly as the water becomes slightly basic. Now if you add a half cup of vinegar, it will overwhelm the baking soda, maybe fizz some, and you will end up with acidic water.
If you put 2 cups of baking soda in a gallon of water, it will still only have a slightly basic pH because baking soda isn't super basic, but you will have a very high alkalinity. If you put the same half cup of vinegar into this water, there won't be enough acid to cancel out all of the baking soda, and you will still have a slightly basic solution.
(Please note, actual science not included, so don't try this and report back)
Some things, like limewater, have a high pH, so configuring your controller to stop adding kalk if the pH gets too high is a good safeguard.
Sent from my SAMSUNG-SM-N920A using Tapatalk
pH is potential of hydrogen, or, is the water acidic or basic.
Alkalinity is additional info about how much acid/base it will take to get the pH to change.
If you have a low alkalinity, like putting a teaspoon of baking soda in a gallon of pure water, it will raise the pH slightly as the water becomes slightly basic. Now if you add a half cup of vinegar, it will overwhelm the baking soda, maybe fizz some, and you will end up with acidic water.
If you put 2 cups of baking soda in a gallon of water, it will still only have a slightly basic pH because baking soda isn't super basic, but you will have a very high alkalinity. If you put the same half cup of vinegar into this water, there won't be enough acid to cancel out all of the baking soda, and you will still have a slightly basic solution.
(Please note, actual science not included, so don't try this and report back)
Some things, like limewater, have a high pH, so configuring your controller to stop adding kalk if the pH gets too high is a good safeguard.
Sent from my SAMSUNG-SM-N920A using Tapatalk
blanden.adam
Team RC
I disagree. People use a pH probe because it tells you about pH. People use alkalinity tests because it tells you about alkalinity. They are both pieces of information that are important in their own right. It's not as though pH would become unimportant if a good, inexpensive, alk probe were available. But, of the two, I'd agree that alk is more important.
With pH, the general rule is that you are looking for stability. It doesn't matter so much what the number is, but you want it to be between 7.8-8.4 or so.
With alk, you are also looking for stability, but it is more appropriate to have a "number" in mind. Different people have different opinions, but it's generally accepted that between 7-12 dKH is acceptable.
So, the two interact, but they are distinct. They generally tell you different things (e.g. alk tells you about calcifying organisms and how much stuff they are taking from the water, pH is more a reporter of the carbon dioxide level or, if you dose kalk, the rate of kalk dosing). For a reef tank, I think it's a better idea to test them separately and interpret them separately.
To be clear, do not use a pH controller to dose kalk, except to have a "high limit" as a safety measure. Always guide dosing with alk testing
. Good luck!
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