My new tank experience managing CO2 and pH

[Morpheosz]

Hey gang,

Just thought I'd share my learnings with my new 75 attempting to get my pH to a good range by controlling CO2. I've tried a number of things so this may be useful for others.

TL;DR: findings:
Indoor air: 7.8 to 7.95
Outdoor air: 7.98 to 8.05
CO2 scrubber air: 8.1 to 8.2

I have a new 75 that sits in my office with very good flow / surface agitation, and a 34g sump in the basement with a Reef Octopus Essence S-130 skimmer which should be a good size for the tank as far as I can tell. I have a refugium that is well lit off cycle from the main tank, but being a new tank, the chaeto ball is pretty small, but I have grown a decent amount of hair algae in the sump. The tank is looking great for a 2 month old tank, and I even have ~75% coralline coverage on the upper most rockwork in the tank already (started with bare rock, a couple live rock from my old tank, and seeded with the algae barn coralline bottles). Also the fuge bottom has about 30% coralline coverage. My alkalinity has varied but I've been able to dial it in right around 7.9 - 8 (started higher and let it slowly decline to 8, doing triton).

In the process of all of these experiments, I bought a CO2 monitor to check my environment and found my basement, where the sump and skimmer are, is a pretty consistent ~600-650PPM. My office varies greatly from 750PPM-1200PPM depending on whether or not I'm working in there with a closed door or it's empty and the door is open.

When I first set the tank up and for the first few weeks, using only inside air, my pH settled in on a night - day cycle of 7.8 - 7.95.

Aiming to change that for the better, and hearing a lot of people suggest just hooking the skimmer to outside air, I tried that next. I have easy access from my basement where the sump is and I was able to hook up a relatively short 3/4" line outside. I ran that for a few days and it definitely helped, but only brought me up to a night-day range of 7.98 - 8.05, so I gained about a tenth of a point.

Lastly I hooked up a BRS Jumbo CO2 scrubber that I bought over the holiday in my gear buying spree. I hooked it up in a recirculating design, pulling air from the top of the skimmer cup. Over the last few days the pH has settled in on a range of 8.1 - 8.2.

So there you have it, at least in my experiment of one, outside air beats inside air, CO2 scrubber beats outside air. I'm kind of surprised my scrubber isn't doing better as I have gotten the impression that they can really send your pH high to the point of needing to moderate it with fresh air or turning off the skimmer, but mine seems to only just get me into the lower end of the "optimal" 8.1-8.3 range. I'm also surprised my pH was that low to begin with as I don't feel like my CO2 readings are crazy, especially in the basement where the skimmer is. I'll run with this for awhile. Related, as I've been testing alk daily to dial in my dosing, I have noticed a significant uptick over the past week. It could simply be the critical mass of coralline growing, or the higher pH working it's magic to promote higher uptake, or most likely the combination, but it seems like good things are happening!

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for posting your results!

 

[reefandfish85]

I use Co2 scrubber as well and my PH has stayed right around 8.0 at night and 8.25 during days, but if you dose buffer to keep your alkalinity up , you can do it when your PH goes lower. This helps to keep it stable as well

 

[fryman]

Very similar to my experience. Thanks for the report!

I was able to hit constant 8.3 pH using an air pump and diffusers, but honestly I'm not sold on whether that's worthwhile yet. Using the skimmer air intake is pretty easy and definately has an effect.

 

[thewedge]

Thanks for sharing your experience. I bought the single canister scrubber for my 130gal and it only keeps my pH around 7.8 during the day. The annoying this is that if I don't keep up with adding water to it, my pH drops to 7.7 or sometimes slightly below. How often have you had to add water to yours?
When I had my 65 gal, I was able to keep pH at 8.3 by dosing alk using soda ash overnight. With this build I have been using All for Reef since it's very easy and being that I'm working from home all the time I just manually add 25ml a day. I only have about 10 frags so, my demand is not too great. But I know from experience with my other tank that I definitely will get better growth with higher pH. I don't think All for Reef boosts pH the way soda ash did.

 

[Morpheosz]

Thanks for sharing your experience. I bought the single canister scrubber for my 130gal and it only keeps my pH around 7.8 during the day. The annoying this is that if I don't keep up with adding water to it, my pH drops to 7.7 or sometimes slightly below. How often have you had to add water to yours?
When I had my 65 gal, I was able to keep pH at 8.3 by dosing alk using soda ash overnight. With this build I have been using All for Reef since it's very easy and being that I'm working from home all the time I just manually add 25ml a day. I only have about 10 frags so, my demand is not too great. But I know from experience with my other tank that I definitely will get better growth with higher pH. I don't think All for Reef boosts pH the way soda ash did.

So far, I haven't added water to it. I have hooked it up in a recirculating fashion so it's pulling damp air from the skimmer cup. Keep in mind I've only run this for 3 days this way, but so far, I have not had water collect in the scrubber, only some moisture on the wall and the intake tube. I'm hopeful that that's all I get so I don't have to mess with draining it, but if it does collect, I have my scrubber mounted on a wall so I could pretty easily hook a hose to the drain plug in the bottom and into my drain in the basement where it lives.

 

[fryman]

Thanks for sharing your experience. I bought the single canister scrubber for my 130gal and it only keeps my pH around 7.8 during the day. The annoying this is that if I don't keep up with adding water to it, my pH drops to 7.7 or sometimes slightly below. How often have you had to add water to yours?
When I had my 65 gal, I was able to keep pH at 8.3 by dosing alk using soda ash overnight. With this build I have been using All for Reef since it's very easy and being that I'm working from home all the time I just manually add 25ml a day. I only have about 10 frags so, my demand is not too great. But I know from experience with my other tank that I definitely will get better growth with higher pH. I don't think All for Reef boosts pH the way soda ash did.

I don't add water to mine either. I had more trouble with excess water but maybe it is very dry where you live?

I suggest looking into recirculating the air from top of your skimmer back to the CO2 media cannister. Alternatively you can just run an air line from the other end of your cannister to somewhere over your sump, which should be pretty humid.

 

[Morpheosz]

I may have gotten lucky on the moisture thing. Since my scrubber is ~5' above the skimmer, I think a lot of the condensation is happening in the air line and dripping back into the skimmer. As you can see in my scrubber, there is just a bit of condensation inside which could be ideal if it doesn't collect and need draining.

Pardon the gaffer tape, I ordered a 3D printed attachment for the skimmer cup that will make for a more elegant / reliable connection for my air line.

 

[I.AM.MR.MIKE]

I may have gotten lucky on the moisture thing. Since my scrubber is ~5' above the skimmer, I think a lot of the condensation is happening in the air line and dripping back into the skimmer. As you can see in my scrubber, there is just a bit of condensation inside which could be ideal if it doesn't collect and need draining.

Pardon the gaffer tape, I ordered a 3D printed attachment for the skimmer cup that will make for a more elegant / reliable connection for my air line.

I have this same skimmer and designed and 3d printed a cover for the lid to recirculate. My scrubber is now very damp inside and the media lasts much much longer probably 2 months. My PH went from never breaking 8 to 8.2 - 8.5. Funny I also drilled my original skimmer cap and added a float switch but haven't wired it to the new neptune breakout box.

 

[Morpheosz]

I have this same skimmer and designed and 3d printed a cover for the lid to recirculate. My scrubber is now very damp inside and the media lasts much much longer probably 2 months. My PH went from never breaking 8 to 8.2 - 8.5. Funny I also drilled my original skimmer cap and added a float switch but haven't wired it to the new neptune breakout box.

Very cool, what did you get for the 3D printed cover if I might ask? Also, out of curiosity, what is your tank size and alkalinity? I'm very curious to compare notes with such a similar build!

 

[Brian_68]

And dosing Kalk daily brought mine even higher with outside air for the skimmer as well.

 

[mdb_talon]

Thanks for sharing results. I wonder what it would do to ph to run the outside air through co2 scrubber prior to skimmer.

 

[Morpheosz]

Thanks for sharing results. I wonder what it would do to ph to run the outside air through co2 scrubber prior to skimmer.

My hypothesis is that it wouldn't be better than the recirculating design for 2 reasons: 1) I assume that the already scrubbed air is lower in CO2 than outdoor air (I could be wrong) and 2) I'm in MN and it's winter so the air outside is very cold and dry so I think you'd lose even more efficiency drying out the media.

 

[mdb_talon]

My hypothesis is that it wouldn't be better than the recirculating design for 2 reasons: 1) I assume that the already scrubbed air is lower in CO2 than outdoor air (I could be wrong) and 2) I'm in MN and it's winter so the air outside is very cold and dry so I think you'd lose even more efficiency drying out the media.

I tend to agree, but just dont remember ever seeing anyone do that in comparison to others would be interesting to see

 

[Morpheosz]

I tend to agree, but just dont remember ever seeing anyone do that in comparison to others would be interesting to see

Well, I have the outside air line installed just sitting there, I'll give it a try!

 

[Morpheosz]

Outside air line connected. Today's pH range was 8.12 - 8.24. Will report back tomorrow night!

 

[fryman]

I tend to agree, but just dont remember ever seeing anyone do that in comparison to others would be interesting to see

I've tried it. Pulling outside air through my CO2 scrubber had a slight reduced effect on pH and consumed media faster than recirculating the air.

 

[Morpheosz]

I've tried it. Pulling outside air through my CO2 scrubber had a slight reduced effect on pH and consumed media faster than recirculating the air.

Cool, thanks for sharing! Just before turning in for the night, I went downstairs to check on things one last time and noticed that since I hooked up to the very cold dry outside air the bottom inch of my media turned dark purple so I decided to kill the experiment.

 

[captainbeardly]

I’m doing a PH experiment as well. I tried the airline from outside to the intake of the scrubber and had the same negative effect on PH. So I reconfigured my scrubber into a recirculating scrubber and my PH stayed at 8.0-8.15 according to my Hydros monitor and double checked with a good old manual tester. So I was thinking why not pump even more fresh air into and see if it changes? So I picked up a cheap air pump, a small plastic container, tubing, and an air stone. Placed the air pump outside in the small plastic container with holes drilled in the side and not the top in case it rains or anything. Ran the air line tubing with the air stone to my sump and it boosted my PH to 8.25-8.28. So I think the combination of outside air and a CO2 scrubber is really a good way to go!

 

[Morpheosz]

I’m doing a PH experiment as well. I tried the airline from outside to the intake of the scrubber and had the same negative effect on PH. So I reconfigured my scrubber into a recirculating scrubber and my PH stayed at 8.0-8.15 according to my Hydros monitor and double checked with a good old manual tester. So I was thinking why not pump even more fresh air into and see if it changes? So I picked up a cheap air pump, a small plastic container, tubing, and an air stone. Placed the air pump outside in the small plastic container with holes drilled in the side and not the top in case it rains or anything. Ran the air line tubing with the air stone to my sump and it boosted my PH to 8.25-8.28. So I think the combination of outside air and a CO2 scrubber is really a good way to go!

Very cool, great idea, thanks for sharing! I've already created that exact type of air pump housing out of a smalll rubbermaid style bin for my pond air pump that runs through the winter. I think I'd want to come up with something to contain the aeration though, like the skimmer does, as I don't want salt spray all over. Did you do anything to contain your bubbles?