An Easy Way to Increase Your Tank's pH with a CO2 Scrubber

Discussion in 'Do It Yourself (DIY)' started by CJO, Mar 9, 2011.

  1. CJO

    CJO Well-Known Member

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    A common issue among aquariasts is that their tank has a lower than desired pH. Many tanks commonly dip to a pH of 7.8 or even lower at night. Although, to the best of our knowledge, this isn't low enough to harm the inhabitants of your aquarium, it does slow down the growth of your corals.

    The low pH is generally caused by excess carbon dioxide (CO2) in the system for various reasons. Common causes are the buildup of organics in a system, living in an energy efficient (fairly air-tight) house, and the use of a calcium reactor.

    There are several ways of combating the problem. Many people grow macro algae in a refugium on an opposite light cycle from their main tank. The macro algae uses the CO2 during the light periods to create energy (remember photosynthesis?). Others dose with kalkwasser, which both adds calcium and alkalinity to the system and raises its pH. I was doing both of these things but was still having issues with low pH.

    That's when I read about the use of a CO2 scrubber. What's a CO2 scrubber? Very simply, it's a container that holds soda lime. When you run air through the container, the soda lime binds with the CO2. This is commonly used in scuba diving rebreathers and in air lines for patients under anathesia.

    In aquariums, it is very easy to connect the container to the air intake of your skimmer so that no extra carbon dioxide is going into your system. Most people who run CO2 scrubbers report a 0.2 to 0.3 increase in their average pH.


    Parts/tools needed-
    • pelletized soda lime
    • a clean, clear plastic container with cap
    • drill
    • drill bits
    • super glue
    • silicon
    • airline tubing that fits your skimmer's air intake
    • beer
    • screws (optional)
    • C-clamp (optional)
    • hacksaw (optional)
    How to begin- first you need to source your soda lime. The soda lime needs to be in a pellatized form. The powder form can easily get into your system and it is quickly used up. It is also good to get they type that changes color when it binds with the CO2 so that you know when to change it out. I've heard that some people get theirs from a scuba dive store, but that it is expensive. mdb_talon mentions below that he purchased his from a dive store for around $75 for a 5 gallon bucket. I purchased mine from National Airgas, a welding supply store. They call it Sofnoline, which I think is a typo on Sofnolime, the brand name. Some people have paid around $120 for a 5-gallon bucket. I was quoted $80, but was able to talk them down to $60. It should be enough to last me for a year or two.

    [​IMG]

    If you want to just buy a smaller amount, Eynonreefer sourced a 3 lb bag for $7.50 JOR553 - Soda Lime, 3 lb. bag in Anesthesia Products at Med-Vet International

    Next, you need a container to hold the pellatized soda lime. You can use any clean, clear plastic container that you find around your house. I used an empty Gatorade container.

    [​IMG]

    You need to drill small holes in one end of the container for the air to come in. Make sure that the holes are small enough that the soda lime can't fall through and make sure that there are enough of them so that the air is not overly restricted.

    [​IMG]

    On the other end, drill a hole in the cap large enough so that the airline just fits. Push it in a little way and use superglue to temporarily hold it (superglue dries fast, but doesn't do a good job of adhereing to these plastics). Then, use silicon to seal both sides of the interface between the airline and the cap.

    [​IMG]
    While you are waiting for the silicon to dry, you can decide where you want to put your container. If you have a large enough area under your tank, you might be able to just stand it up anywhere. My cabinet is fairly tight, so I used some screws and cut a plastic C-clamp in half to create a small holder for the container over the cabinet doors.

    [​IMG]

    Once the glue is dry, fill the container with soda lime, put on the top and connect the other side of the airline to your skimmer's air intake.

    [​IMG]

    I connected my CO2 scrubber a few weeks ago and the low point of my pH has gone from 7.8 up to 8.0.

    Before CO2 Scrubber
    [​IMG]

    After CO2 Scrubber
    [​IMG]
    I hope this helps some people out. Please let me know if you have any questions or comments.

    CJ
     
    Last edited: Apr 21, 2011
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  2. mdb_talon

    mdb_talon Well-Known Member

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    Good writeup thanks. Just as a side not I got 5 gallons of the lime for around $75 from a dive shop so it can be affordable there as well think it depends on the dive shop.

    I have been using a scrubber for over a year and have noticed about a .3 ph increase. Combining this with sump lights on alternating cycle I have managed a PH that ranges from 8.1/8.2 to 8.5 throughout the day/night cycle. I am still working to try to stabilize that range better maybe 8.3 to 8.5, but with the scrubber I am in much better shape than I was before.
     
  3. CalmSeasQuest

    CalmSeasQuest Well-Known Member

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    Great writeup CJO

    I experienced a .20 increase in pH. One note, some Tunze skimmers (i.e. Tunze DOC 9000 series) draw air internally and will require the use of an air pump to push air through the CO2 scrubber into the skimmer using the Ozone port.
     
  4. CJO

    CJO Well-Known Member

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    Thanks, guys. Updated the post with pictures.

    CJ
     
  5. Paul_N

    Paul_N MOD R2R Supporter

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    Very nice! I have been wanting to try this.
     
  6. VegasRick

    VegasRick Well-Known Member R2R Supporter

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    Nice write up. I was looking into a co2 scrubber, it seems the main ingredient in the Sofnolime is calcium hydroxide with some type of color changing added to see when its exhausted. There was also mention of using zeolyte in another thread.
    Did the scrubber restrict the airflow to the skimmer? any negative effects?
     
  7. CJO

    CJO Well-Known Member

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    If it restricts it, it hasn't been enough to be noticeable. I do not know of any significant negative effects and did quite a bit of research on it before setting up my own. Many people report that it increases the skimming production, though I haven't really noticed it.

    CJ
     
  8. mooo

    mooo Member

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    definitely gonna try this out.
     
  9. firsttime

    firsttime Well-Known Member

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    Very nice write up!!!!
     
  10. frankthetank

    frankthetank Well-Known Member

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    Nice wright up CJ.
    I got a reactor think ill try it out.
     
  11. VegasRick

    VegasRick Well-Known Member R2R Supporter

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    Might have to try it myself, thanks for the info
     
  12. mooo

    mooo Member

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    from your graph it looks like after a week or two we'd have to replace it again..
     
  13. skinz78

    skinz78 Moderator Staff Member Team R2R R2R Supporter R2R Excellence Award Partner Member

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    Great thread! I will be trying this as soon as I can source soda lime.
     
  14. CJO

    CJO Well-Known Member

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    That depends on how much CO2 is in your air and how much air your skimmer uses. I'm about at a month now and haven't had to replace mine yet. The dips at the ends of my graphs are from when I changed out the kalkwasser and had to wait for it to settle before restarting my ATO. Also, even if I had to change it every other week, the amount is still minimal.

    CJ
     
  15. ReefDreams

    ReefDreams Well-Known Member

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    This looks very interesting. Thanks for the write up, im gonna have to give this a try.
     
  16. CJO

    CJO Well-Known Member

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    quick bump

    CJ
     
  17. Eynonreefer

    Eynonreefer Well-Known Member

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    Rhinohorn420 and Vibora like this.
  18. Tabasco1

    Tabasco1 Well-Known Member

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    CJO-man, nice write up. Thank you so much for taking the time to puting this together.
     
  19. CJO

    CJO Well-Known Member

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  20. CJO

    CJO Well-Known Member

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    Thanks. I just changed out my bottle of soda lime this past weekend for the first time. Looks like one bottle lasted about 1-1/2 months for me. I think I have a large enough supply for years!

    CJ
     
    BluewaterLa likes this.

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