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How to Make a CO2 Scrubber to Raise pH

It’s that time of year, when it’s freezing outside and toasty inside.  That means many houses (especially newer ones) start to accumulate carbon dioxide (CO2).  For aquarists, this often translates into a reduced pH during the winter.  Rather than opening a nearby window or adding potentially troublesome supplements, here’s an inexpensive and easy solution!

Supplies:

  • Soda Lime (I purchased mine from  Amazon:  Jorvet J0553 Soda Lime Bag, 3-Pound)
  • Filter Floss
  • Small piece of bridal veil material
  • Skimmer or other pump to pull air through the scrubber
  • Open endcap
  • Gasket for open endcap
  • Endcap for screw-in connection
  • Screw-in connector that will fit into your vinyl tubing and the outlet endcap
  • Vinyl tubing to fit your skimmer air intake (I used 1/2″ OD)
  • ABS Tube (or PVC if you prefer)
  • Weld-on ABS Glue

Instructions:

  1. Figure out where you want to mount your scrubber.  Due to space constraints, I could only fit it horizontally.  You will have better performance if you mount it vertically (due to the way the media will settle).  This will also help you determine the size of your scrubber.  If you have a small space, make a small scrubber.  If you have a large tank and lots of space, go with a large one!  This is a flexible project!
  2. Get your supplies based off your initial design.  I used a 12 inch long section of ABS Schedule 40 pipe.

    ABS Tubing

    ABS Tubing

  3. Place the bridal veil between the gasket and the intake endcap.  Secure it.  I used superglue.  Weld-on is probably more appropriate.

    Inlet Endcap

    Inlet Endcap

  4. Attach the intake endcap to the tube with Weld-on.

    Inlet Endcap

    Inlet Endcap

  5. Attach the outlet endcap to the tube with Weld-on.
  6. Add the screw-in connection to the output endcap of the tube.

    Outlet Connection

    Outlet Connection

  7. Stuff a bit of filter floss down into the tube by the outlet.  This will prevent media from entering the skimmer.

    Filter Floss in Output

    Filter Floss in Output

  8. Fill the tube with media, leaving an inch for more filter floss at the intake side.

    JorVet Soda Lime

    JorVet Soda Lime

    CO2 Scrubber Filled with Soda Lime

    CO2 Scrubber Filled with Soda Lime

  9. Stuff filter floss in the intake side.  This will prevent media from falling out the intake.

    Input Filled with Filter Floss

    Input Filled with Filter Floss

  10. Place the intake endcap on the tube.

    Input Endcap Cover

    Input Endcap Cover

  11. Add the vinyl tubing to the outlet connector.

    Vinyl Tubing

    Vinyl Tubing

  12. Now you have a completed scrubber!

    Completed CO2 Scrubber

    Completed CO2 Scrubber

  13. Place the scrubber in its new home by your tank.  I used hangers.

    Scrubber Hangers

    Scrubber Hangers

  14. Connect the other end of the vinyl tubing to the air intake of your skimmer.

    CO2 Scrubber Attached to Skimmer Air Intake

    CO2 Scrubber Attached to Skimmer Air Intake

  15. Over the next several days, watch your pH.  It should raise.  You can either watch your controller to know when to change the media, or you can use color-changing media (mine turns to purple when exhausted.)

    pH Before and After CO2 Scrubber

    pH Before and After CO2 Scrubber

Hints:

  • Use a clear cylinder if you have one so it is easier to see the media change color.
  • You can do this project with any empty container – a drink bottle, two-part container, et cetera.  My prototype was with a Gatorade bottle!
  • You may need to increase the flow rate of your skimmer’s air intake.  The CO2 scrubber adds flow restriction to the air, so you may need to compensate.
  • There’s no need to copy my design completely.  Size yours for your size tank and pH requirements.
  • This is not limited to wintertime pH problems.  You could use this where a higher pH is required for certain treatments.

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