Different take on a CO2 scrubber for your tank.

[Neil Fox]

So I have been reading about CO2 scrubbers and since I use them in the course of my work, I thought I would make a few improvements on the current design and document them here.

This time of year, people are indoors more and this can have an adverse affect on our water quality. An increase in CO2 increases the acidity of the water and lowers pH. A CO2 scrubber is an easy way to mitigate this but it needs to be done correctly for it to be effective. One of the biggest problems is the media drying out; commercial CO2 scrubbers used in Saturation Diving Chambers normally have a means of spraying the media with water to keep it working. If the humidity drops below 55% the sodalime simply doesn't work. Normally the chamber atmosphere in a diving system is monitored carefully to keep the humidity at around 55 to 60% and CO2 levels essentially at zero. Any CO2 increase is an indication of either exhausted media or dry media. Since most of us don't have a humidity sensor, I took a low tech approach, using moisture sensing strips that change from blue to pink in the presence of moisture.

The other thing that I did was design a container with a reticulated foam disk in the base and a lid modeled after a Mason Jar that feeds the incoming air into the base of the container. To get the humidity up I add 10ml of water into the inlet periodically with a syringe when the indicator strip turns blue.

The assembly is attached to my skimmer using 3/8" silicone tubing. I ordered the CO2 scrubbing media from the same supplier we use at work, diving grade with a built in white to violet indicator, choosing the same grade that is used in lung powered emergency scrubbers. This has some properties that are ideal for our reef tanks, as it doesn't restrict flow, will not break down if it gets wet and doesn't break down and create dust, as an extra precaution I added a layer of vacuum paper over the outlet to keep dust out of the tank water.

So far, the results have been quite positive, I am setting up a couple of experiments to demonstrate the efficacy of the design, I will post them here later. The jar holds about 32 oz. of media (roughly 900 grams), though any jar with a 90mm opening should work with my lid design. It is worth pointing out that tank size will have nothing to do with the life of the media, this is a function of the air your skimmer movers though it and the CO2 in the room. So far I have been running the initial jar for about 11 days and it is still working using a Reef Octopus INT200 on a 120 gal reef. I don't have an Apex so I have to rely on spot checks but evening and morning tests have been positive. If anything, I have had to disconnect during the day if pH becomes to high, so a am planning on adding an inlet solenoid off a controller. For now though, I just wanted to share my design with everybody. I will be more than happy to answer any questions about it and will add more details about how you can make your own or how to get the parts.

 

[laverda]

What media are you using? I have been planning to build a CO2 reactor for a while now.
Could one be used to remove CO2 from an RO/DI system before it goes to the DI resin?

 

[Neil Fox]

What media are you using? I have been planning to build a CO2 reactor for a while now.
Could one be used to remove CO2 from an RO/DI system before it goes to the DI resin?

Hi laverda. I am using Sofnolime. Basically they are the only producer of CO2 scrubbing media on earth. Their parent company Molecular Products recently purchased the HP Sodasorb company and promptly discontinued that product, leaving only Sofnolime, they also subsequently doubled the price! Not sure how that doesn't violate antitrust laws. As far as using it for RO/DI systems, it is basically a vapor phase media in this form. I'm pretty sure if you ran water through it it would spike your alkalinity, since it's very basic. I am not sure how it would work in that capacity.

 

[laverda]

Thanks for the info.

 

[pfoxgrover]

Great Thread! Thanks for the info! I love the idea of the humidity indicator. I just ordered a few.

I set mine up as partially recirculating and seem to have a bigger problem with too much moister. But I do seem to still burn through it pretty fast.
-If the media gets wet does that kill it?
-Another thought I had was contact. Since the media never clogs, is it fair to assume all of the media is being depleted or just a channel through the media?

I also made a DIY reactor. Mine is made out of an OXO spaghetti container. I crated a void in the bottom for separating the media from water and a fill/drain port. The plastic was very brittle so I had to be super careful drilling it.

 

[pfoxgrover]

I tried out on of the humidity indicator strips in my last batch and never really saw a distinct color change anywhere. If I had to guess I might have seen a little pink. Mine is set up semi-recirculating and is probably getting too much moisture so maybe I am off the chart on the high side.