Using CO2 removal media to remove CO2 from the air going into your protein skimmer is one of the most efficient ways to increase pH in your reef aquarium when too much dissolved CO2 is suppressing your tank’s pH. We already have some excellent videos on how to raise pH in a reef tank with an entire episode dedicated to CO2 scrubbers.


Back in 2017, we followed a post by Reef2Reef user Velcro who described a recirculating type installation of a CO2 scrubber that results in a much more efficient use of the CO2 removal media compared to the traditional installation.


Traditional vs Recirculating CO2 scrubber installation


Recirculating BETA vs. Traditional CO2 Scrubbers

A standard CO2 scrubber installation on your protein skimmer pulls air from the room around your tank so it is constantly scrubbing new air. The result is often scrubbing way more air than is necessary to achieve your goal of increasing pH in your reef.


In a closed off area like a fish room this may be less impactful but in a living room with open doors and walkways to the rest of the house, new air will always be pulled into the scrubber. That's not inherently bad, but it will exhaust the media and require that you change it out quite often especially if it is not controlled in any way.


The recirculating concept solves this issue by recycling the air from your skimmer that is already scrubbed of CO2 resulting in a much longer lifespan of the CO2 removal media.


Recirculating CO2 scrubber installation diagram


How to install a BETA recirculating CO2 Scrubber

The skimmer pump is drawing air through the CO2 scrubber, the air mixes with water to create bubbles inside the skimmer and when the bubbles pop the air is typically released through the holes on the lid of the protein skimmer.


Collectio cup lid with scrubber tubing port


Instead of letting that air escape, create a port in the protein skimmer lid and secure the tubing going back into your CO2 scrubber. The scrubber will then draw air from your collection cup at all times instead of from the surrounding environment. Since this air is already scrubbed free of CO2, the skimmer can no longer introduce new CO2 and the CO2 media will last much longer.


Reef2Reef Thread


Why BETA?

This idea came from a post on Reef2Reef and we noticed three common setbacks that multiple early adopters are reporting. Without having extensive hands on experience, we are calling it BETA because it has room for refinement and further investigation.


We do suspect it will become quite popular as more reefers try it, share their experiences and come up with ways to overcome some of these setbacks. The idea is certainly effective and potentially resolves one of the biggest setbacks of using a CO2 scrubber which is the cost of media.


CO2 scrubber with ball valve control


When pH gets too high...

In some cases, the recirculating design works too well and the pH gets too high. You should be able to remedy this with a wye fitting and valve which lets fresh air into the mix.


Solenoid valve on CO2 scrubber inlet for air control


You can do this manually with a simple ball valve but you might also consider an electronic solenoid attached to your aquarium controller to open and close based on the tank’s pH level.


In this case, the media savings may very well be outweighed by the investment in valves which do wear out over time. An alternative would be to bypass the wye fitting and valve altogether and simply shut down the skimmer when pH is too high via a pH controller. A skimmer does not necessarily have to run 24/7 to be effective and the benefits of a perfectly stable pH would likely be better than losing a few hours of skimmer performance.


Overflowing protein skimmer


When the skimmer overflows...

We all know that skimmers can go nuts if something gets into the water that increases viscosity such as an accidental overdose, fish or coral fatality, or simple overfeeding.


If the cup is filled with foam, this could potentially allow the scrubber to draw the wet foam into the scrubber chamber. If it does, the water can dissolve the media which gets sucked into the skimmer and therefore into your tank water. This will sky rocket the pH and there is also a dye in the media so liquifying that and dosing it to the tank is a bad idea.


Methods of preventing fluid from getting into Co2 scrubber


You might consider a foam pre-filter inside the skimmer cup at the end of the tubing to diffuse the foam before it can get sucked into the scrubber. A float switch connected to a controller that shuts down the skimmer when the cup is full is a more full proof remedy.


Protein skimmer drain fitting


You could also use the drain port on the collection cup which then drains skimmate into an external container. The external collection chamber can then be outfitted with a switch to shut down the skimmer when it is full.


For double protection in any of these cases, an aquarium controller with a high pH alarm to shut down the skimmer will also ensure you never run into trouble.


Jumbo CO2 Scrubbers


When water gets in the way...

If you let it run long enough without maintenance, it is possible for humidity to collect in the bottom of the scrubber. Humidity is actually good for the media performance and longevity but you don’t want so much to collect that it builds up and submerges the media.


Fluid inside the CO2 scrubber for any amount of time is a bad idea.


The build up of humidity to the point of needing to be drained should really only happen when your media lasts a really long time or you forget to swap it out. The larger scrubber chambers will require this less frequently and our jumbo units have a convenient drain port on the bottom to make it easy.


If this method is not for you or you simply wish to learn more, be sure to check out our video TOP 5 Tips: How to raise pH in reef tanks or check out the BRStv Investigates episodes in which we start to prove that elevated pH and major elements have a significant impact on coral growth.



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