Questions from observations after using CO2 absorption material

[jent]

I have never had pH issues, usually between 8.1 and 8.3 as measured by the apex. After getting new windows it has been a bit closer to the lower end, so I recently changed my skimmer to use the CO2 absorption materials sold by BRS in hopes of getting closer to the 8.4.

I was resistant to the idea / costs until I saw the idea to make the gas recirculating (pulling the intake of the material from inside the skimmer collection lid).

This worked better than expected, too good in fact! At night the pH wont drop at all, it stays completely flat. And then during the day the pH would climb as normal. Once I was easily hitting 8.5 I knew I needed to re-think this.

I plan to use a solenoid with the apex to enable fresh air intake into the simmer and see if I can achieve a mostly flat 8.4 pH. However until that's done I have been manually disconnecting the material to keep the pH from climbing too high. I notice that my pH falls way faster than ever before, and falls lower than it used to without the help of the material.

Which brings me to my questions...
What chemically is happening in this material, is it just an absorption of the carbon to instead leave o2 post reaction?

Any way to rationalize why a tank might become dependent on this, and otherwise loose even more pH without it?

I worry there is some reaction going on with my alk or something else I am not understanding. I am trying to decide if I should just abandon the idea, or if I should move forward with the solenoid to control the pH.

Thanks everyone!

 

[Jeeperz]

Let me see if I have this correct. You run a line from inside the collection cup to the co2 media, then back to the intake for the skimmer? How long does your co2 media last?

 

[Snoopy 67]

While I can't comment on the chemistry ( over my head) chasing PH is a waste of time . Absolutely nothing wrong with a PH of 8.

 

[jent]

Let me see if I have this correct. You run a line from inside the collection cup to the co2 media, then back to the intake for the skimmer? How long does your co2 media last?

Correct, I was going to take photos and post my findings when I have it working smoothly. The lid holes are currently siliconed shut, but this will change once I add the solenoid for fresh air. When the solenoid is in place the plan is for there to be a Y before the skimmer intake, the side with the material will always be open, the other side will open by the apex whenever we reach our target pH to keep it from climbing further. I expect with the lid holes removed when the solenoid is open very little air will want to pass through the resistance of the material.

There is still a very big unknown, which is I have an AC pump skimmer. I used to restrict the air flow a little, and it just happened the resistance of the material matched about how much resistance I was adding already. I worry the solenoid will complicate tuning my skimmer. Either way it has been a fun test.

I don't know how long the material will last yet, only been playing with it for about 2 weeks now. So far the color changing material has not indicated any wear.

 

[Quietman]

O2 is 21% in atmosphere, CO2 is normally in range of hundredths of percent (.04% - .08% in buildings). The media just removes CO2 with a negligible effect on O2.

System dependent on higher pH? Sure, but isn't that true of all parameters that reach optimum values. Lose pH more if higher initially? Yes, but it has farther to fall. pH without media (or other ways to raise like kalk) is still going to be determined by CO2 in household air and tank aeration (degassing CO2 in water to match air) and that isn't impacted by where you start from. Floor is still set by environmental factors.

I have always thought the solenoid valve was a rather elegant solution to keep pH from swinging day/night if using CO2 scrubbing media in canister.

I tend not to worry about any of this though natural reefs have daily and seasonal pH swings and as long as my tank is >7.8, I'm pretty happy. I'm also not interested in maximizing growth rates beyond what I can achieve without all the extra gear. I'm lucky though that my pH stays in the 7.85-8.1 range.

 

[jent]

Lose pH more if higher initially? Yes, but it has farther to fall.

Sorry, maybe I was not clear. So for example last night I left the material disconnected, I expected it to fall to ~8.1 like it used to. Instead I found the tank below 8.0 this morning. So I worry that simply disconnecting the material would result in a pH drop further than it used to go naturally somehow. That is why I worry there could be some kind of dependency developing that I am not understanding.

 

[Quietman]

I see...more a temporary drop to lower values than normally expect. Hmm... I'll need others to check my thinking. First not sure I'd go to reduction of CO2 long term initially as cause since household CO2 concentrations can vary widely and I'd suspect that as most likely along with instrument calibration.

That said...and here's where I'm theorizing so don't trust this...high pH should use up buffer faster so if CO2 increased then the impact to pH could be higher resulting in a temporarily lower pH until buffer readjusted through dosing or water change.

 

[Randy Holmes-Farley Verified Community Expert]

Sorry, maybe I was not clear. So for example last night I left the material disconnected, I expected it to fall to ~8.1 like it used to. Instead I found the tank below 8.0 this morning. So I worry that simply disconnecting the material would result in a pH drop further than it used to go naturally somehow. That is why I worry there could be some kind of dependency developing that I am not understanding.

That seems unlikely.

 

[Randy Holmes-Farley Verified Community Expert]

That said...and here's where I'm theorizing so don't trust this...high pH should use up buffer faster so if CO2 increased then the impact to pH could be higher resulting in a temporarily lower pH until buffer readjusted through dosing or water change.

If alk dropped lower than usual due to faster consumption, then swings in pH both up and down can become larger.

 

[jent]

After measuring alk that seems to be it. I was down to 5.1! Normally I target for 8, and things have been stable enough I only have been testing every couple weeks. I assume the sudden drop is from increased growth, but either way I should have been testing it more after making the change.

Thanks for the advice