DIY: CO2 Diffuser

Written by emmalise mac
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DIY: CO2 Diffuser
Keep aquarium plants healthy by diffusing CO2 into the water. (Aquarium image by crossgolfing from

Dissolved carbon dioxide (CO2) promotes aquatic plant growth in aquarium habitats. Added CO2 helps plants to flourish and is essential for plant propagation for sale. Homemade yeast-based CO2 production systems provide a low-cost alternative to CO2 tanks, but require effective CO2 diffusers to relieve pressure. Most importantly, undissolved CO2 will rise to the surface as bubbles and escape and will not improve the aquarium environment. You can create a simple, DIY CO2 diffuser in less than an hour from inexpensive materials available at any aquarium supply store.

Skill level:

Things you need

  • Aquarium powerhead pump with 1/2-inch diameter outlet tube
  • 1-inch diameter to 1/2-inch diameter tubing connector
  • Clear silicone aquarium sealant
  • 1-inch diameter gravel cleaner
  • Air line tubing - standard 3/16-inch external diameter
  • Small air stone - 1/2 to 3/4 inch total length
  • Coarse filter foam
  • Drill
  • 3/16-inch diameter drill bit
  • Suction cup clips for 1-inch diameter tube (e.g., heater clips)
  • Utility knife

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  1. 1

    Remove the plastic cap and attached tubing from the gravel cleaner -- you will need only the 1-inch diameter vacuum tube.

  2. 2

    Apply a thin, 1/4-inch wide band of clear silicon sealant around the outside of one end of the vacuum tube. Insert that end of the vacuum tube into the large end of the 1-inch diameter to 1/2-inch diameter tubing adaptor. Allow to dry thoroughly, according to the sealant manufacturer's instructions.

  3. 3

    Drill a hole into one side of the vacuum tube, approximately two inches from the open end.

  4. 4

    Insert one end of the air line tubing into the hole drilled in the vacuum tube. Push the air line tubing through the vacuum tube until the air line tube comes out of the open end of the vacuum tube. Attach the air stone securely to the end of the air line tubing. Pull the air line tubing back through the drilled hole so that the air stone is suspended horizontally inside the tube.

  5. 5

    Apply clear silicon sealant around the air line tubing to seal any gaps between the tubing and the hole drilled in the vacuum tube. Allow sealant to dry thoroughly, according to the manufacturer's recommendations.

  6. 6

    Cut a 1-inch by 1-inch square of coarse filter foam. Insert the filter foam into the open end of the vacuum tube, so that the foam rests just below the air stone.

  1. 1

    Attach suction cup clips to the vacuum tube.

  2. 2

    Install the powerhead pump in the aquarium. Position the outlet parallel to the aquarium wall.

  3. 3

    Connect the 1/2-inch diameter end of the tubing connector on the vacuum tube to the 1/2-inch diameter outflow tube on the powerhead pump.

  4. 4

    Connect the air line tubing to the CO2 source. CO2 will begin to enter the vacuum tube.

  5. 5

    Turn on the powerhead pump. CO2 will dissolve in the water from the outflow in the vacuum tube before the water enters the aquarium, and the foam will prevent large bubbles from escaping.

Tips and warnings

  • Connect the inflow from an external filter to the diffuser instead of using a powerhead pump.

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