ph as a hint to alkalinity?

boxfishpooalot

New member
Hi Randy,

Whenever I check my alkalinity and if it is lower say at 2.4meq/l the ph is usually 8.0-8.07 . Is this a decent way to know when to add suplementation? If I keep my alkalinity above 3meq/l the ph is above 8.10 . This seems to work fine with baking soda.
 

bertoni

Premium Member
That's one of those tests that will work until some part of the systems changes a bit, and then it'll lie to you. I think it's worth testing alkalinity if you want to know the current value.
 

DrBDC

New member
I have to say that on a softy tank I have, that I would just add a cup of each two part solution (the homemade version) whenever I saw the pH get down to 8. Everything in that tank did great and when I did test I was right on. But,,,,, that was all softies and only a couple lps (candycane and frogspawn). So I only had to add once a month or so. Very very little ca/alk consumption. If there were anything using ca/alk I would be adding so much it woiuld have to throw the numbers off very quickly.
 

palmerc

New member
As long as you keep to the same supplement this can give an indication.

However if you change alkalinity supplements or switch between various ones ofeten then this will not work as eg. sodium carbonate will have a lot higher pH than sodium bicarbonate for the same alkalinity added.

Clinton
 

Randy Holmes-Farley

Reef Chemist
Premium Member
The other issue is that as the seasons change and the indoor CO2 level changes, what you though was suitable may not longer be.

But I do use pH monitoring as a rough guide to whether I am adding adequate limewater. That is not something that you can give someone detailed directions for, just something that can be learned about a particular system in a particular home over a long period of seeing the correlation.
 

boxfishpooalot

New member
If the system doses only sodium bicarbonate what is the maximum ph attainable with Co2 equilibriated at an alkalinity of 2.5meq/l?

Would borate drastically change values?
 

Randy Holmes-Farley

Reef Chemist
Premium Member
Borate at normal levels will not impact the pH/alkalinity/CO2 relationship. If the air has a normal amount of CO2 and the water is equilibrated with it, the pH will be 8.2. :)
 
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