New c02 mete, low ph

[Doob]

Good day! My newer tank has had chronically low ph, that’s gone even lower since upgrading to a HE furnace in the home. It’s been struggling to hit 8 during the day, and bottoms out under 7.7.

A new ph meter arrived today, an Aranet 4, initial readings are around 1200ppm.

For those of you with the data, are these numbers similar to what you see in your tanks?

When they’re installed the furnace I also got a quote for an ERV, but they were aggressively trying to talk me out of it. They didn’t understand my motivation behind it though.

I bought the meter just to confirm my suspicion that this is the root cause, and to justify the ERV.

 

[Randy Holmes-Farley Verified Community Expert]

A tank in a room with 1200 ppm CO2 will run about 0.47 pH units lower than the same tank run in 400 ppm CO2 (outside) air, assuming everything else is identical and no outside air is used.

 

[rishma]

in this thread I describe using outdoor air to combat indoor CO2….
https://www.reef2reef.com/threads/m...-outdoor-aeration-ph-boost-stability.1084802/

 

[rishma]

A tank in a room with 1200 ppm CO2 will run about 0.47 pH units lower than the same tank run in 400 ppm CO2 (outside) air, assuming everything else is identical and no outside air is used.

Can you show how this is calculated?

 

[rishma]

Pretty please @Randy Holmes-Farley

 

[Randy Holmes-Farley Verified Community Expert]

Sure.

There is a direct linear relationship between the concentration of H+ and the equilibrium level of CO2 (Or H2CO3, hydrated CO2 = carbonic acid) in the water.

Likewise, the equilibrium level of CO2 in the water is directly linearly related to the CO2 in the air.

Thus, if CO2 rises by a factor of 3 from 400 to 1200 ppm, then H+ rises by a factor of 3.

Since pH is -log[H+], then pH changes by a factor of log(3) =0.477 .

 

[rishma]

Sure.

There is a direct linear relationship between the concentration of H+ and the equilibrium level of CO2 (Or H2CO3, hydrated CO2 = carbonic acid) in the water.

Likewise, the equilibrium level of CO2 in the water is directly linearly related to the CO2 in the air.

Thus, if CO2 rises by a factor of 3 from 400 to 1200 ppm, then H+ rises by a factor of 3.

Since pH is -log[H+], then pH changes by a factor of log(3) =0.477 .

Thanks for this. Remarkably simple.

Since my tank pH nighttime minimum without massive air is say 8.0 and with massive air is 8.3, that means the CO2 concentration in the water is about 2x higher without outdoor air aeration. Do I have that right?

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for this. Remarkably simple.

Since my tank pH nighttime minimum without massive air is say 8.0 and with massive air is 8.3, that means the CO2 concentration in the water is about 2x higher without outdoor air aeration. Do I have that right?

Yes. :)

 

[rishma]

Yes. :)

Awesome! I don’t know what I will possibly use this knowledge for but I sure am happy to have it. Thank you.

 

[Doob]

After collecting just a few days of data, it appears that my c02 levels are quite a bit lower than I thought. During the week it doesn’t seem to get much over 700. Probably higher on the weekends. I’m going to rest the meter directly on the tank for a while, but I don’t think this justifies bringing in outside air.

 

[rishma]

After collecting just a few days of data, it appears that my c02 levels are quite a bit lower than I thought. During the week it doesn’t seem to get much over 700. Probably higher on the weekends. I’m going to rest the meter directly on the tank for a while, but I don’t think this justifies bringing in outside air.

Agree that’s not very high indoor CO2, but it is probably close to 1.5x outdoor CO2. Per Randy’s math above the potential pH benefit is near 0.2. That’s actually a big pH change to me, though I cannot argue it’s worth doing.

One thing you could do to verify the potential pH benefit is to take a cup of tank water in the morning, note the pH, and then aerate it outside for a few hours with an airstone. Then measure pH of the aerated water.

 

[rishma]

I really like the idea of a CO2 meter, i found the one you are using on Amazon. You like it?

 

[Doob]

I really like the idea of a CO2 meter, i found the one you are using on Amazon. You like it?

I do like it. It’s Bluetooth only so you can’t check levels while you’re away, but it logs the data so when you get back you can see the trends. The display is similar to a kindle, not an LCD type display, so it looks and feels very high in quality. Connection was flawless and the app is so far bug free.

I bought it direct from the manufacturer for the same price, they shipped quick. Always gotta advise against amazon….