PH sky high after adding CO2 scrubber.

richarddeweerd · May 24, 2021

Last Saturday night I added a CO2 scrubber (mainly to try to silence the skimmer air intake), but now I'm not so sure if I need it.

After connecting it to the skimmer my PH went sky high to 8.60 which it is normally between 8.10 and 8.25. I definitely need to do a PH sensor calibration check before I can do another test.

I'm now doubting if the high PH, and subsequently, the lower CO2 levels in the water are limiting a) coral growth and b) the effectiveness of my chaeto reactor. So for now I removed it again which you can see directly in the APEX log.

T-J · May 24, 2021

Your numbers were fine before the scrubber. If it were me, I'd just run it at night.

Clownfishy · May 24, 2021

That does look a bit weird as you have a massive increase during the day but then it plummets during the night. Clearly pH goes down at night is normal but with such a massive increase adding the pH scrubber, I am confused why it dropped so much during the night. Do you know your C02 levels in your house? Also, are you drawing air from outside through the media first or drawing air from the room.

I get to 8.5 - 8.6 in the summer months when we have all our windows open (I live in the UK) so this year, I am thinking of diverting the intake on those specific days so it is not drawing through the C02 media or just drawing it through the media at night.

I have not experienced such a hike in pH levels by just adding media.

richarddeweerd · May 24, 2021

It did not plummet until I removed it when the PH was 8.6

Billldg · May 24, 2021

Are you controlling it with a solenoid to turn it on and off? If not then I would install a solenoid to turn the scrubber on and off.

richarddeweerd · May 24, 2021

My Apex does not have enough outputs at the moment and the energy bar is not in stock for a while already.... so currently it is not possible.

I can also add a t-splitter so only a part of the air comes through the scrubber.

richarddeweerd · May 25, 2021

@Randy Holmes-Farley I've read your articles about high and low pH, and I come to the conclusion that a pH of 8.6 with my current Alkalinity of 3 meq/L (I try to keep it at 3.2 meq/L) and a calcium level of 400 ppm means that the tank is leaning to a CO2 deficit when I put the scrubber in place.

I'm guessing that a CO2 deficit causes growth problems in all photosynthetic organisms both my corals and algae is that true?

Without the scrubber my pH is between 8.1 and 8.3 that means that the Co2 is slightly elevated during the night. But I'm not sure if this is a real issue. Personally I'm a fan of the KISS approach and I think that all unnecessary software, devices and other electronics cause only more variables and therefore more possible issues. So'm thinking of removing the scrubber completely

Randy Holmes-Farley · May 25, 2021

CO2 deficit (high pH) is not really known to cause a problems in reef tank since many organisms use bicarbonate for their CO2 source in seawater.

If the measurement is correct, I wouldn't keep using as much media since pH 8.6 is going to begin to cause more and more calcium carbonate precipitation.

Acroalan · May 25, 2021

I found a tip from someone else, so this is not original with me. But I set up a virtual outlet on my Apex that kicks on at a PH of 8.4 and off at 8.35. Then set my skimmer to turn off when virtual PH outlet is active and on when not. I only had to run a CO2 scrubber in winter though and now that windows are open all day I removed it and my PH stays 8.2-8.4 on its own pretty much.

Randy Holmes-Farley · May 26, 2021

Acroalan said:
I found a tip from someone else, so this is not original with me. But I set up a virtual outlet on my Apex that kicks on at a PH of 8.4 and off at 8.35. Then set my skimmer to turn off when virtual PH outlet is active and on when not. I only had to run a CO2 scrubber in winter though and now that windows are open all day I removed it and my PH stays 8.2-8.4 on its own pretty much.

My concerns with on/off skimmer are two fold:

1. You are not getting potentially useful oxygenation when it is off.

2. If off for too long, any water remaining in the skimmer plumbing may become stagnant and possibly even product hydrogen sulfide. That's a bigger concern with folks who try to run, say, only during the night or some such thing.

Acroalan · May 26, 2021

Excellent points that I had not considered. Thank you for bringing them up.

piranhaman00 · May 26, 2021

richarddeweerd said:
My Apex does not have enough outputs at the moment and the energy bar is not in stock for a while already.... so currently it is not possible.

I can also add a t-splitter so only a part of the air comes through the scrubber.

Just get an amazon smart bar with dc selenoid it ball valve

richarddeweerd · May 26, 2021

Randy Holmes-Farley said:
the measurement is correct, I wouldn't keep using as much media since pH 8.6 is going to begin to cause more and more calcium carbonate precipitation.

The precipitation can be an issue. I thought I had a pH calibration bag in stock, (I normally have calibration fluids for all my sensors that need calibration) but I've run out. I'll get it this week when I'm at my LFS

arking_mark · May 26, 2021

Randy Holmes-Farley said:
My concerns with on/off skimmer are two fold:

1. You are not getting potentially useful oxygenation when it is off.

2. If off for too long, any water remaining in the skimmer plumbing may become stagnant and possibly even product hydrogen sulfide. That's a bigger concern with folks who try to run, say, only during the night or some such thing.

Hmmm...I run my scrubber based on pH and haven't noticed these issues, but maybe I'll program it to come on every couple of hours to avoid these scenarios.

arking_mark · May 26, 2021

arking_mark said:
Hmmm...I run my scrubber based on pH and haven't noticed these issues, but maybe I'll program it to come on every couple of hours to avoid these scenarios.

Looking at my dissolved O2 for the last week, I'm seeing lows of 6.9 and highs of 7.2. I'll try to see if these correlates with Skimmer activity. I do believe these levels are at or near saturation for 35ppt salinity and 77 degrees temp.

arking_mark · May 26, 2021

arking_mark said:
Looking at my dissolved O2 for the last week, I'm seeing lows of 6.9 and highs of 7.2. I'll try to see if these correlates with Skimmer activity. I do believe these levels are at or near saturation for 35ppt salinity and 77 degrees temp.

Initial analysis shows that the highs corellate more with the light cycle and the lows right before the skimmer kicks on.

Randy Holmes-Farley · May 26, 2021

arking_mark said:
Initial analysis shows that the highs corellate more with the light cycle and the lows right before the skimmer kicks on.

That makes sense. Nightly low is my concern about O2. During the day it may even be supersaturated.

richarddeweerd · May 27, 2021

Indeed, as far as I know with my very limited knowledge of biology and chemistry, O2 is a product of photosynthesis were light is used to change CO2 in O2 and C. And the carbon is used for the plant/coral to grow. That’s is why I’m thinking that too low CO2 can’t be good. But I’m just an amateur on this.

There are a few big greenhouses in my area that actively pump in CO2 to increase plant growth.

Randy Holmes-Farley · May 27, 2021

richarddeweerd said:
Indeed, as far as I know with my very limited knowledge of biology and chemistry, O2 is a product of photosynthesis were light is used to change CO2 in O2 and C. And the carbon is used for the plant/coral to grow. That’s is why I’m thinking that too low CO2 can’t be good. But I’m just an amateur on this.

There are a few big greenhouses in my area that actively pump in CO2 to increase plant growth.

That can be true in freshwater, but not so much in seawater, where many photosynthetic organisms use plentiful bicarbonate as their source of CO2, not actual CO2.

I discuss that here:

Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley - Reefkeeping.com