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I thought my pH drop was 1.2 but it was 2.0. Can this be right?

MarcusA

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3 Apr 2022
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19
Location
usa
I have been measuring the pH drop in my tank to estimate how much CO2 I need to inject, aiming for a drop of 1.2.

However, I recently read that I should be measuring the tank water after it has degassed for 24 hours. Previously, I had simply been taking samples from the tank without any degassing process.

Using my Apera pH meter on the degassed water, I found that my pH drop was not 1.2 but 2.0! (8.5 to 6.5) As I understand it, this gives me a CO2 concentration of 300 ppm. Is this even possible? How are my shrimp alive?

Background info:

I have a 20 gallon tank and use a cerges reactor with a bubble rate of more than 2 bubbles per second. The tank has a spraybar across the back with lots of surface movement.

The tank has shrimp and snails in it. The number of shrimp has been steady and they seem more or less healthy. They are not proliferating, but once in a great while I see a berried female.

The plants seem fairly healthy and grow quickly, and they pearl. The tank has some minor algae, including algae on the plants.

My pH meter is an Apera PH60, one year old, just calibrated before the measurement. I store the probe in the cleaning solution. The tank water measurements do take a long time (10-15) minutes to stabilize.

Using the Photone app, for whatever it's worth, I measured my PAR at substrate at something like 90.
 
Using my Apera pH meter on the degassed water, I found that my pH drop was not 1.2 but 2.0! (8.5 to 6.5) As I understand it, this gives me a CO2 concentration of 300 ppm. Is this even possible? How are my shrimp alive?

regarding pH of 8.5 for degassed water --- what is the pH of the water you use for water changes?
 
Hi all,
Using my Apera pH meter on the degassed water, I found that my pH drop was not 1.2 but 2.0! (8.5 to 6.5) As I understand it, this gives me a CO2 concentration of 300 ppm.
I'm not a great fan of pH meters, it isn't that pH isn't very important (it is), it is just that it is <"quite tricky to measure accurately">.

Same for me, then you have a <"solution of known dKH">. You won't have 300 ppm CO2, because the pH ~ carbonate ~ CO2 chart only "works" at 4dKH.

How hard is your water? The CO2 / pH values are dependent upon the <"carbonate hardness (dKH) of your water">. It would be possible to have soft alkaline water, with a pH of pH 8.5 if your water company added a strong base like <"sodium hydroxide (NaOH)">.

cheers Darrel
 
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Thank you all so much for responding.

@erwin123, my tap pH came back as 10.07. My city's water report says the average is 9.70.

@dw1305, The tank KH is 8.5 per the API liquid test. The KH out of the tap is 3. I wonder why my tank water so much higher. I change the water 50% twice a week. I do have some bootleg "seiryu stone" that I got from amazon in there.

I've been adding a teaspoon of Seachem Equilibrium to the tank with water changes, which is supposed to raise gh without affecting kh and ph. In the past, I was having anemic growth and thought I would cover my bases in regards to calcium and magnesium. Not sure if it helps at all.

I have a drop checker somewhere. Hopefully the solution hasn't gone bad or something. I'll set that up today hopefully.

Thanks again, everybody.
 
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Hi all,
@erwin123, my tap pH came back as 10.07. My city's water report says the average is 9.70.
@dw1305, The tank KH is 8.5 per the API liquid test. The KH out of the tap is 3. I wonder why my tank water so much higher. I change the water 50% twice a week.
That is the NaOH addition by your city, it is designed to stop copper (Cu) and lead (Pb) (from old pipes) <"going into solution"> in your, naturally soft, water.
I've been adding a teaspoon of Seachem Equilibrium to the tank with water changes, which is supposed to raise gh without affecting kh and ph. In the past, I was having anemic growth and thought I would cover my bases in regards to calcium and magnesium.
I'd guess that is more "Equilibrium" than you need. Have a look at <"James's Planted Tank"> for some DIY options.

Plants have got a small calcium (Ca) requirement, but do need some magnesium (Mg). Yellow leaves can be caused by magnesium and/or iron (Fe) deficiencies, you need to look at <"which leaves (old or new) are chlorotic">.

cheers Darrel
 
Well, I installed a drop checker. It settled on a yellowish green, but not fully yellow. So that is reassuring.
I'm still not sure why the pH drop is so drastic.
@dw1305, thank you for your help. I'm in the States, and I've just read that the water in my city naturally has a high pH because it flows through a lot of limestone. I managed to find a version of my city's water report that actually lists magnesium, and it averages about 15 mg/L at the tap. Calcium is similar. Do you think I can stop using the equilibrium?
 
Hi all,
I've just read that the water in my city naturally has a high pH because it flows through a lot of limestone.
Same for me for our tap water, straight from a limestone aquifer and about 17 dKH and 17 dGH.
I managed to find a version of my city's water report that actually lists magnesium, and it averages about 15 mg/L at the tap. Calcium is similar.
Something is still a bit strange, because that <"isn't much calcium (Ca)">. The magnesium (Mg) content is for <"geological reasons">.
Do you think I can stop using the equilibrium?
Yes.

cheers Darrel
 
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