Recirculating Co2 Skimmer Reminder/Warning

piranhaman00

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Hello, something very interesting I noticed on my tank recently that has been pointed out by @Randy Holmes-Farley and others as a warning.

160 gallons, lids on DT, air exchange is probably mostly through skimmer.

I was running a Lifereef skimmer through a Co2 scrubber in recirculating fashion. Getting amazing results increased growth and had about 0.3-0.4 increase in pH.

Recently started having nutrient issues so I decided to throw on another skimmer I had laying around. I set this skimmer to draw air from the collection cup of the Lifereef, so although the air wasn’t going directly through a reactor it was pulling air that had been through a reactor at one point.

I had another pH bump and less of a dip at night, also nutrients are raising much slower so I was very happy.

Couple of days passed and my corals looked bad but the biggest thing that stood out was my big lion was on the sand bed breathing heavy. I dipped a few other fish for flukes and came up with nothing. I had also added a new wave maker so I figured the Lion was tired from swimming against current. I took out power head but that didn’t help.

After several large water changes and nothing helping the corals or Lion I thought about the scrubber. I remember reading about the O2 saturation issues with recirculating. I hooked up the second skimmer to draw pure ambient air and opened a window to get fresh air in. This is not normally ideal due to the current heat, but in basement it’s not that big of issue.

Not 24 hours later the corals were open and the Lion is completely fine again, swimming around with slow respirations. My eel also started eating much more aggressively that she has in the past few months, coincidentally when I added the Co2 scrubber in recirculating fashion.

I think in my case adding the second skimmer brought the air to water gas exchange closer to equilibrium but with recirculating this was detrimental because there was no new O2 entering the system.

This will obviously not pertain to everyone running recirculating, my tank is pretty heavily stocked and with glass lids so most gas comes in via skimmer.

I don’t believe there is a hobby grade test that is accurate enough to measure O2 saturation but I found this extremely interesting, as this was clearly an issue I was experiencing.

I now keep window open, AC has to fight a little more but that’s alright, with one skimmer recirculating and the other pulling ambient air (with window open) I am having great pH results and corals and fish are able to breath again!

This whole ordeal lasted about 14 days, from hooking second skimmer , up to seeing negative results to fixing.

I will state again though, tank looks better than before running the recirculating skimmer initially, I would urge people doing this to run their skimmer without the scrubber and see if there is a response in the tank from getting more oxygen.

Fun times.
 

shakacuz

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once i upgrade to my 75 (or 90G if i can find a cheap used tank near me) i will be recirculating my skimmer with fishofhex's attachment. this was a good heads up for me, thanks!
 

Randy Holmes-Farley

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Hello, something very interesting I noticed on my tank recently that has been pointed out by @Randy Holmes-Farley and others as a warning.

160 gallons, lids on DT, air exchange is probably mostly through skimmer.

I was running a Lifereef skimmer through a Co2 scrubber in recirculating fashion. Getting amazing results increased growth and had about 0.3-0.4 increase in pH.

Recently started having nutrient issues so I decided to throw on another skimmer I had laying around. I set this skimmer to draw air from the collection cup of the Lifereef, so although the air wasn’t going directly through a reactor it was pulling air that had been through a reactor at one point.

I had another pH bump and less of a dip at night, also nutrients are raising much slower so I was very happy.

Couple of days passed and my corals looked bad but the biggest thing that stood out was my big lion was on the sand bed breathing heavy. I dipped a few other fish for flukes and came up with nothing. I had also added a new wave maker so I figured the Lion was tired from swimming against current. I took out power head but that didn’t help.

After several large water changes and nothing helping the corals or Lion I thought about the scrubber. I remember reading about the O2 saturation issues with recirculating. I hooked up the second skimmer to draw pure ambient air and opened a window to get fresh air in. This is not normally ideal due to the current heat, but in basement it’s not that big of issue.

Not 24 hours later the corals were open and the Lion is completely fine again, swimming around with slow respirations. My eel also started eating much more aggressively that she has in the past few months, coincidentally when I added the Co2 scrubber in recirculating fashion.

I think in my case adding the second skimmer brought the air to water gas exchange closer to equilibrium but with recirculating this was detrimental because there was no new O2 entering the system.

This will obviously not pertain to everyone running recirculating, my tank is pretty heavily stocked and with glass lids so most gas comes in via skimmer.

I don’t believe there is a hobby grade test that is accurate enough to measure O2 saturation but I found this extremely interesting, as this was clearly an issue I was experiencing.

I now keep window open, AC has to fight a little more but that’s alright, with one skimmer recirculating and the other pulling ambient air (with window open) I am having great pH results and corals and fish are able to breath again!

This whole ordeal lasted about 14 days, from hooking second skimmer , up to seeing negative results to fixing.

I will state again though, tank looks better than before running the recirculating skimmer initially, I would urge people doing this to run their skimmer without the scrubber and see if there is a response in the tank from getting more oxygen.

Fun times.

Thanks for the info!
 

VelocityTech

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Would love to see some more details on this subject! Great information, thanks! Wondering if anyone has done any experimenting with these? Even with hobby grade test kits.. We could get a general idea. I was debating on making my skimmer recirculate the air. And this thought came up in the back of my head, which led me here. Wonder if mixing it a few times a day via solenoid, would fix any negative effect.
 

Randy Holmes-Farley

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I do not recommend a fully recirculating skimmer for the reasons in this thread: low O2. That said, partial recirculating and partly fresh air should be ok.
 

Dan_P

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Hello, something very interesting I noticed on my tank recently that has been pointed out by @Randy Holmes-Farley and others as a warning.

160 gallons, lids on DT, air exchange is probably mostly through skimmer.

I was running a Lifereef skimmer through a Co2 scrubber in recirculating fashion. Getting amazing results increased growth and had about 0.3-0.4 increase in pH.

Recently started having nutrient issues so I decided to throw on another skimmer I had laying around. I set this skimmer to draw air from the collection cup of the Lifereef, so although the air wasn’t going directly through a reactor it was pulling air that had been through a reactor at one point.

I had another pH bump and less of a dip at night, also nutrients are raising much slower so I was very happy.

Couple of days passed and my corals looked bad but the biggest thing that stood out was my big lion was on the sand bed breathing heavy. I dipped a few other fish for flukes and came up with nothing. I had also added a new wave maker so I figured the Lion was tired from swimming against current. I took out power head but that didn’t help.

After several large water changes and nothing helping the corals or Lion I thought about the scrubber. I remember reading about the O2 saturation issues with recirculating. I hooked up the second skimmer to draw pure ambient air and opened a window to get fresh air in. This is not normally ideal due to the current heat, but in basement it’s not that big of issue.

Not 24 hours later the corals were open and the Lion is completely fine again, swimming around with slow respirations. My eel also started eating much more aggressively that she has in the past few months, coincidentally when I added the Co2 scrubber in recirculating fashion.

I think in my case adding the second skimmer brought the air to water gas exchange closer to equilibrium but with recirculating this was detrimental because there was no new O2 entering the system.

This will obviously not pertain to everyone running recirculating, my tank is pretty heavily stocked and with glass lids so most gas comes in via skimmer.

I don’t believe there is a hobby grade test that is accurate enough to measure O2 saturation but I found this extremely interesting, as this was clearly an issue I was experiencing.

I now keep window open, AC has to fight a little more but that’s alright, with one skimmer recirculating and the other pulling ambient air (with window open) I am having great pH results and corals and fish are able to breath again!

This whole ordeal lasted about 14 days, from hooking second skimmer , up to seeing negative results to fixing.

I will state again though, tank looks better than before running the recirculating skimmer initially, I would urge people doing this to run their skimmer without the scrubber and see if there is a response in the tank from getting more oxygen.

Fun times.

Hanna sells an oxygen test kit. Method is straightforward, though following directions is important. I have used it over the years. If water testing is a chore or mystery to you, maybe skip this test.
 

Randy Holmes-Farley

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Does the CO2 scrubbing media absorb O2 as well?
No. The concern is trapped recirculating air cannot ever add O2 to a system that can become low O2 at night.
 

Projects with Sam

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No. The concern is trapped recirculating air cannot ever add O2 to a system that can become low O2 at night.
Nitrogen party!
Blue Velvet Oxygen GIF
 

ChrisfromBrick

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I am getting green cyano in my display. I wonder if this is the result of recirculating and the lack of O2 Randy spoke of. I am going to try opening a basement window at the expense of this awful humid weather and see if that makes a difference.
 

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