THE BEST WAY to implement a CO2 scrubber!

Randy Holmes-Farley

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My skimmer is running at night. Outside air is still added to the skimmer

Its been ~30 years since my chemistry days in college.. but if all of the O2 was depleted in the system the skimmer would be less efficient, fewer bubbles would be produced, and eventually, a vacuum would be formed due to the missing the oxygen...

but again... it's not a sealed system.. Outside air is used. The skimmer is working exactly the same as before (same skimmate produced, same bubble levels, same power consmption.. etc)

Unless you can show that a skimmer uses 100% of the air sucked into the venturi I don't think I have anything to worry about. If anything my skimmer is adding more PURE O2 into the tank than before at night.

Those statements are not correct. CO2 can be entirely stripped from low O2 air and the air can still be low in O2. CO2 is a very minor component of air. Most of it is N2. People mistakenly think O2 and CO2 always move in opposite directions. Not true. Both can be high, both can be low, or any combination of high and low.

Perhaps an analogy is useful. Say you are in a room with only 95% of the normal amount of O2 in it. If you remove a book from the room, the total O2 will rise if normal air replaces its volume, but the air is still deficient in O2. Maybe it is now 95.1% of normal.

No one is claiming the O2 is all gone. 95% of normal is undesirable (IMO).
 

TheLost

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Those statements are not correct. CO2 can be entirely stripped from low O2 air and the air can still be low in O2. CO2 is a very minor component of air. Most of it is N2. People mistakenly think O2 and CO2 always move in opposite directions. Not true. Both can be high, both can be low, or any combination of high and low.

Perhaps an analogy is useful. Say you are in a room with only 95% of the normal amount of O2 in it. If you remove a book from the room, the total O2 will rise if normal air replaces its volume, but the air is still deficient in O2. Maybe it is now 95.1% of normal.

No one is claiming the O2 is all gone. 95% of normal is undesirable (IMO).

Sounds like a great test for somebody like BRS to conduct then.. Since they are recommending the recirculating CO2 scrubbers as a way to solve pH problems :)
 

TheLost

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No one is claiming the O2 is all gone. 95% of normal is undesirable (IMO).

Let me ask you this then.. What would you recommend as a way to raise the pH of my tank. Again, without using a CO2 scrubber my pH is in the low 7.8 - 7.6. If i can keep a window open in the room it gets up to 8.0, but that's not always an option.
 

Randy Holmes-Farley

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Let me ask you this then.. What would you recommend as a way to raise the pH of my tank. Again, without using a CO2 scrubber my pH is in the low 7.8 - 7.6. If i can keep a window open in the room it gets up to 8.0, but that's not always an option.

Outside air for skimmer. Scrubber air that isn’t recirculated. Open windows. High pH alk additives. More photosynthesis.
 
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Lots of people have very successful tanks using lifereef skimmers, which recirculate the air from the collection cup.
 

TheLost

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Outside air for skimmer. Scrubber air that isn’t recirculated. Open windows. High pH alk additives. More photosynthesis.

Outside air is not an option.
Keeping windows open is not an option.
Refugium lights are already running 12+ hours at night.

Which specific High pH alk additive?
 
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Outside air is not an option.
Keeping windows open is not an option.
Refugium lights are already running 12+ hours at night.

Which specific High pH alk additive?
Use Randy's high pH two part recipe if you are comfortable working with sodium hydroxide. Otherwise use kalk in top off. If you don't have high demand for alk though, it will start to accumulate and your alk will go up. I always found too much variability trying to replace my evaporation with kalkwasser and preferred using the sodium hydroxide two part on a doser.
 

TheLost

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Use Randy's high pH two part recipe if you are comfortable working with sodium hydroxide. Otherwise use kalk in top off. If you don't have high demand for alk though, it will start to accumulate and your alk will go up. I always found too much variability trying to replace my evaporation with kalkwasser and preferred using the sodium hydroxide two part on a doser.

Since you are the OP on of this thread.. what are your thoughts now (3 years later) on recirculating air from the skimmer back into the CO2 scrubber?

Am I going to deprive my tank of O2 and everything will die?

Or is it a valid option of keeping pH high in a CO2 filled room?

Stability & reliability is my goal.
 
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Since you are the OP on of this thread.. what are your thoughts now (3 years later) on recirculating air from the skimmer back into the CO2 scrubber?

Am I going to deprive my tank of O2 and everything will die?

Or is it a valid option of keeping pH high in a CO2 filled room?

Stability & reliability is my goal.
It worked great while I used it, but I ended up setting up a new tank that had access to the outdoor air so I took some complexity out of the system by removing the media.

Like I said, there are many successful tanks with skimmers the recirculate air from the cup (lifereef). If you are worried about oxygenation maybe just add a refugium and light some chaeto for a good part of the day.
 

TheLost

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It worked great while I used it, but I ended up setting up a new tank that had access to the outdoor air so I took some complexity out of the system by removing the media.

Like I said, there are many successful tanks with skimmers the recirculate air from the cup (lifereef). If you are worried about oxygenation maybe just add a refugium and light some chaeto for a good part of the day.

I'm going to keep it running for now.. Since its 'sucking' in some outside air to keep my pH in the range I want, and I have good flow at the surface I should be 'OK' (i also have chaeto under light for ~12 hours).

But... What I am going to do is build something to measure the O2 in the 'loop'.

I have an electrochemical O2 air sensor laying around from a project I did a few years ago. I'm going to build a box that sits between the CO2 scrubber and the skimmer and measure/log the levels. I'll probably add a CO2 sensor since they are relatively inexpensive.

Nothing says 'fun project' like a bunch of charts and graphs :)
 

Randy Holmes-Farley

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Am I going to deprive my tank of O2 and everything will die?

Or is it a valid option of keeping pH high in a CO2 filled room?

Stability & reliability is my goal.

Let's not get hyperbolic, shall we.

Since folks run nice reef tanks without skimmers at all, it cannot be worse than that in terms of oxygenation.

That does not mean it is a desirable thing to intentionally elect to have lower O2.
 

Randy Holmes-Farley

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Outside air is not an option.
Keeping windows open is not an option.
Refugium lights are already running 12+ hours at night.

Which specific High pH alk additive?

Hydroxide is by far the best. Kalkwasser (limewater), or a DIY high pH two part using sodium hydroxide. About 2x the effect of carbonate.

Carbonate is second best.

Bicarbonate additives and organic salts (like formate in ALL for Reef) are worst as additives in this regard.

CaCO3/CO2 reactors are the worst way with regards to pH. But they may still be a fine choice.
 

Randy Holmes-Farley

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I'm going to keep it running for now.. Since its 'sucking' in some outside air to keep my pH in the range I want, and I have good flow at the surface I should be 'OK' (i also have chaeto under light for ~12 hours).

But... What I am going to do is build something to measure the O2 in the 'loop'.

I have an electrochemical O2 air sensor laying around from a project I did a few years ago. I'm going to build a box that sits between the CO2 scrubber and the skimmer and measure/log the levels. I'll probably add a CO2 sensor since they are relatively inexpensive.

Nothing says 'fun project' like a bunch of charts and graphs :)

I would be very interested to see O2 in the gas loop compared to O2 when not recycling. :)
 

Miller535

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I ran a scrubber for maybe a few months about a year ago. I personally did not like it. I never got nearly the amount of time out of the media as advertised (many others in reviews say the same), because of the cost of the media and how often you change it, it can quickly be one of the larger expenses on a monthly basis for a tank.

I think if I were to try and use one again, would try and see if it would be possible to the the airline for the skimmer on a splitter. One end just pulling in air from the room and the other pulling in air from the scubber. And put them on solenoids so that the scrubber only turned on at night or if PH dropped below a certain value.
 

Randy Holmes-Farley

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I ran a scrubber for maybe a few months about a year ago. I personally did not like it. I never got nearly the amount of time out of the media as advertised (many others in reviews say the same), because of the cost of the media and how often you change it, it can quickly be one of the larger expenses on a monthly basis for a tank.

I think if I were to try and use one again, would try and see if it would be possible to the the airline for the skimmer on a splitter. One end just pulling in air from the room and the other pulling in air from the scubber. And put them on solenoids so that the scrubber only turned on at night or if PH dropped below a certain value.

It seems to me that people are assuming that recirculating the air will use media more slowly than simple hydration of the untreated home air. At night, recirculating may use more media than ordinary home air just passed over some water to increase the humidity. I'm not sure how effective the equilibration is in each pass of air through a skimmer, but many tanks drop lower in pH than is equilibrium with their home air, and in that case, the media may be used faster in recycling mode rather than letting the skimmer blow off the excess CO2.
 

Miller535

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It seems to me that people are assuming that recirculating the air will use media more slowly than simple hydration of the untreated home air. At night, reciculating may use more media than ordinary home air just passed over some water to increase the humidity. Many tanks drop lower in pH than is equilibrium with their home air, and in that case, the media may be used faster in recycling mode rather than letting the skimmer blow off the excess CO2.

That is because BRS made a video where Ryan said he saw someone online recirculating it and said it made sense to him and has been recommending people to do it. He believes that it starts "rescrubbing the same air". I personally do not believe that at all. He has unfortunately made several videos lately telling everyone to chase 8.2-8.3ph. And that he use to tell people that 7.8-8.3 was fine as long as you were in the range, but now he knows better. And since that I have noticed an influx in post here about ph and C02 scrubbers. And resurfaced post like this one.
 

Randy Holmes-Farley

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That is because BRS made a video where Ryan said he saw someone online recirculating it and said it made sense to him and has been recommending people to do it. He believes that it starts "rescrubbing the same air". I personally do not believe that at all. He has unfortunately made several videos lately telling everyone to chase 8.2-8.3ph. And that he use to tell people that 7.8-8.3 was fine as long as you were in the range, but now he knows better. And since that I have noticed an influx in post here about ph and C02 scrubbers. And resurfaced post like this one.

Thanks. i was hoping someone actually had some, data. lol
 

Miller535

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Thanks. i was hoping someone actually had some, data. lol

Nope, purely a theory. lol. Although I am sure in a community this large there are people who would anecdotally claim it works.

My own anecdotal experience was that my skimmer did not perform as well. I do not think it was getting the same amount of air draw as it did without the scrubber.
 

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Nope, purely a theory. lol. Although I am sure in a community this large there are people who would anecdotally claim it works.

My own anecdotal experience was that my skimmer did not perform as well. I do not think it was getting the same amount of air draw as it did without the scrubber.

Ha... The BRS video is exactly why I set up my recirculating scrubber. I'm going to wait a few months before i decide if its worth it.. but right now things are looking good.

In the past when I used my CO2 scrubber (just the standard BRS setup) i would consume a bag of CO2 Media in under a week.

With the recirculating scrubber setup I've used less than 1/4 of the CO2 media in 2 weeks (I've got painters tape on the canister and I'm marking the level each day).

Right now i have a Y splitter on the intake before the scrubber with a manual ball valve that lets a small amount of outside air into the system to keep my pH from getting above 8.5.

I have an electronic ball valve that I will have automatically open a few times a day... i'm just waiting for The Apex DC24 bare wire cable to show up from BRS.

Pulling the air from the outside isn't an option for me. I would have to run the hose down into the basement, and then go ~30' to the nearest wall. That long of run would have a larger impact on my skimmer performance, even if I ran most of it with a larger diameter PVC pipe. But then i would also have to deal with sub-freezing air in the winter... and 100f heat in the summer.
 

Miller535

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Ha... The BRS video is exactly why I set up my recirculating scrubber. I'm going to wait a few months before i decide if its worth it.. but right now things are looking good.

In the past when I used my CO2 scrubber (just the standard BRS setup) i would consume a bag of CO2 Media in under a week.

With the recirculating scrubber setup I've used less than 1/4 of the CO2 media in 2 weeks (I've got painters tape on the canister and I'm marking the level each day).

Right now i have a Y splitter on the intake before the scrubber with a manual ball valve that lets a small amount of outside air into the system to keep my pH from getting above 8.5.

I have an electronic ball valve that I will have automatically open a few times a day... i'm just waiting for The Apex DC24 bare wire cable to show up from BRS.

Pulling the air from the outside isn't an option for me. I would have to run the hose down into the basement, and then go ~30' to the nearest wall. That long of run would have a larger impact on my skimmer performance, even if I ran most of it with a larger diameter PVC pipe. But then i would also have to deal with sub-freezing air in the winter... and 100f heat in the summer.

The Y alone would make the media last longer.

And again I never claimed it didn't work, just that I don't buy into the theory, and that there is no real data behind it. And if you look at my response a few post back, I said if I were to try it again I would basically do what you have said. I think the y and the split air will have more of an affect on making the media last longer then the recirculating. But anything's possible.
 

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