Tuning a Skimmer / CO2 Scrubber for pH Control

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Does all of your top off come through the kalk reactor?

Interesting that you you attribute 0.1 increase in pH to kalk. I guess I would have expected more. This is really valuable information.

It seems like oversizing the skimmer really has helped with CO2 exchange.

Would you mind pulling data from your controller logs to get a % time skimmer on with CO2, % time skimmer on with room air, % time skimmer off?

I know you mentioned earlier in the thread that you're less interested in the skimmer for filtration and more interested in it for pH control. I think this is the right idea. I have run many tanks (even large tanks!) with no skimmer. That being said, do you still get some skimmate production with this setup?

Thanks for taking the time to post this thread. It's incredibly useful. I feel like many CO2 scrubber threads are from people who have seen only marginal increases in pH and have not been successful in setting up in a way that manages both pH and moderates scrubber media consumption.

I'll try to pull the skimmer scrubbing info. However, my estimate is that it's on 4-12hrs a day depending on home CO2 levels. Usually around 8hrs.

You can actually calculate pH impact of kalkwasser drip and you made me want to figure it's actual impact.

Per @Randy Holmes-Farley :
"In my experiments, adding 0.5 meq/L (1.4 dKH) of hydroxide (equivalent to 1.25% of the tank volume of saturated limewater) boosted the pH of new IO salt mix (alk about 11 dKH) by about 0.66 pH"

I'm adding about .8dKH and .8% by volume. So I'm guessing I should be getting about .42 increase in pH per day or 0.017 per hour. Anecdotally, I believe my average pH is about a 0.1 higher. Looking back at some old notes just dosing Kalkwasser appears it may have a slightly higher boost to the tank like 0.12.

I guess I could turn off my skimmer for a couple of days and see where things settle to. Then similarly stop the Kalkwasser for a couple days and see that as well.

I can say, when my skimmer was off line for a day or so,, my pH dropped to a low of 8.12 from a normal low of 8.24.

So it could be that I'm getting something around 0.12ph boost from both Kalkwasser and CO2 scrubbing skimmer.

My tank prior to pH boosting was usually between 7.9 and 8.0. Adding ~0.24 gets me close to where I am now. The reverse lighting refugium boosts a little as well....so maybe those # are close enough.

I attribute the low boost from others who implement CO2 scrubbers is due to it not adequately out competing the other sources in their tank...i.e. their power heads and such are doing a good job aerating their tank with high CO2 air.
 
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Chrisv.

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I'll try to pull the skimmer scrubbing info. However, my estimate is that it's on 4-12hrs a day depending on home CO2 levels. Usually around 8hrs.

4-12 hours of scrubbed air and then off for the remaining time?
I attribute the low boost from others who implement CO2 scrubbers is due to it not adequately out competing the other sources in their tank...i.e. their power heads and such are doing a good job aerating their tank with high CO2 air.
Wow, so skimmer size really does matter here when it comes to overcoming home CO2 levels. Neat.
 

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My setup is not quite the same as arking_mark but pretty similar. I just turn off the skimmer when pH is over 8.3. This is my ph vs skimmer trend.

The jump 10Oct is because I replaced the co2 scrubber media. I should also mention I changed my low setpoint on 11 Oct from 8.25 to 8.28.

20211014_093354.jpg
 
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My setup is not quite the same as arking_mark but pretty similar. I just turn off the skimmer when pH is over 8.3. This is my ph vs skimmer trend.

The jump 10Oct is because I replaced the co2 scrubber media. I should also mention I changed my low setpoint on 11 Oct from 8.25 to 8.28.

20211014_093354.jpg
Awesome.

I can't pull Skimmer on times from my GHL. ;(
 
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My setup is not quite the same as arking_mark but pretty similar. I just turn off the skimmer when pH is over 8.3. This is my ph vs skimmer trend.

The jump 10Oct is because I replaced the co2 scrubber media. I should also mention I changed my low setpoint on 11 Oct from 8.25 to 8.28.

20211014_093354.jpg
This is very useful! It clearly demonstrates that old reactor media vs new media (I.e. not scrubbed vs scrubbed) makes a substantial difference.

How often do you have to change out the media?

Do you dose kalk or other pH raising additives?
 

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This is very useful! It clearly demonstrates that old reactor media vs new media (I.e. not scrubbed vs scrubbed) makes a substantial difference.

How often do you have to change out the media?

Do you dose kalk or other pH raising additives?
Yes it does. I have to replace the media about every 2-3 weeks. Before recirculating it was less than one week. The media still doesn't last as long as I'd like. This time I only filled the reactor about 60% to see if this affects how long the media lasts. Even when not full it has no trouble keeping my pH pretty tightly controlled.

I dose saturated kalk about 2liters/day during night hours. I also have a refugium on reverse photo-period with relatively small amount of ulva and red ogo macroalgae. I think this and the kalk helps elevate night pH a bit but I don't think as significant as co2 scrubbing media. Although I haven't tested without these online so not really sure
 
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