Excess CO2 & Low pH

bcarl77 · Aug 30, 2017

Hi all,

I have been able to determine my tank has a buildup of co2. Peak pH is around 7.9, Min is about 7.65. I live in a new high efficiency apartment in Florida so we cannot open the windows often due to the high humidity and heat. I took a cup and airated inside the apartment and got a pH of 7.5, did the same thing on a window ledge drawing only outside air and got 8.1.

I have a small tank with a nano skimmer, I am temporarily located next to a window so I was able to my skimmer intake to outside air, however this did not seem to impact pH overnight. I also have a HOB filter and Jebao pump for surface agitation. Is it possible the skimmer is not drawing enough air to overcome the surface agitation?

I have looked into a Co2 scrubber and I am going to try it. I am hesitant on effectiveness if the skimmer is not drawing enough air to overcome the surface agitation. Is there a way to create a loop to extend the media life or any other ideas to extend the life of the media?

Any other ideas I can do to help remove the co2?

Randy Holmes-Farley · Aug 30, 2017

Small tanks are the hardest to maintain normal pH in the face of high CO2 in the air because there is so much surface area (e.g., tank top) relative to the water volume.

Humidifying the incoming air (if needed) can increase media life.

A loop to recycle the skimmer outlet air might be useful since the removal of CO2 from seawater is a slow process and it may not come to equilibrium with a single pass through a skimmer.

bcarl77 · Aug 30, 2017

Something like this? So instead of scrubbing the incoming air to just the skimmer you air scrubbing all the Co2 leaving the tank and putting clean air in?

Randy Holmes-Farley · Aug 31, 2017

Yes, although the drawback is O2 equilibration, which will stop.

bcarl77 · Sep 1, 2017

Here is the final product. Some interesting results so far. I started running it at about 6pm last night. Turned my HOB filter down to minimize surface agitation. Noticed that some water (very small amount) was still getting through. When I got home at about 11 the pH was 7.95, highest night reading I've seen.

I wanted to minimize water contact with the beads so I removed the media and installed filter pads in the bottle to soak up any moisture that came through. I was quite encouraged at the pH so I turned the HOB back up to full.

Woke up this morning with a pH of 7.7... I turned the HOB back down and have seen the pH increase a little (display light is turning on) to 7.75.

Is the scrubber working??

bcarl77 · Sep 7, 2017

So an update here.

The Co2 media will not change color and the pH is still at 7.65 in the morning. I am not sure if the skimmer is pulling enough air for this to actually be effective.

I currently have the tank located in my bedroom. I have noticed at nights in the evenings when I shut the door and go to sleep the pH will being to drop otherwise it will stay stable. pH will stay around 7.75 on nights when I am sleeping there and pH is 7.65 when both my finance and I are sleeping.

I have had issues using the recycled air approach as I cannot get the line to stop sucking up foam from the skimmer since the collection cup is so small.

The refugium doesn't seem to have helped much. I am not sure if my low-power planted LED is strong enough.

I am in FL and preparing for this storm, I also move here in 2 weeks and the tank will move to the living room. I will reassess when the tank gets in it's new location and hope things are better.