How to Make a DIY CO2 Reactor For an Aquarium

The addition of CO2 into a fish tank allows hobbyists to grow an assortment of beautiful plants in the aquarium. Unfortunately, store-bought, pressurized, CO2 injection can be very expensive and complicated to set up. Adding your own homemade CO2 reactor to an aquarium requires very little cost to build or maintain, and the materials needed to keep it running are easily obtained at a local grocery store.

Things You'll Need

  • 2-liter plastic bottle
  • Electric drill
  • Silicone airline tubing
  • Aquarium silicone
  • Needle-nose pliers
  • 1/2 teaspoon active yeast
  • 2 cups sugar
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Instructions

    • 1

      Thoroughly clean and dry a two-liter soda bottle and cap.

    • 2

      Determine the hole size to drill in the cap by placing a drill bit into one end of the silicone tubing; the drill bit should be just slightly too big to easily fit into the tube opening (The reason for doing this is that all silicone tubing is not manufactured the same, and for the snuggest fit, it is best to check your individual tube diameter in this fashion).

    • 3

      Drill a hole in the center of the bottle cap using the drill bit you have decided on.

    • 4

      Cut one end of the silicone tubing on a 45 degree angle, and pull that end through the hole in the cap to a length of about two inches using needle-nose pliers.

    • 5

      Run a bead of aquarium silicone around the tubing on both sides of the cap, being careful not to get silicone on the cap threads.

    • 6

      Allow the cap to dry at least 24 hours.

    • 7

      Fill the bottle 3/4 full with lukewarm tap water.

    • 8

      Add two cups of sugar and 1/2 teaspoon active dry yeast to the bottle and shake well.

    • 9

      Screw the cap firmly on the bottle.

    • 10

      Run the other end of silicone tubing into your tank, and connect it to the intake of a canister filter, or to a store-bought CO2 diffuser. Alternately, you can use a 3-inch piece of bamboo chopstick inserted into the output of your DIY CO2 reactor line. The hollow structure of the bamboo will act as a diffuser, forcing numerous tiny CO2 bubbles out into your tank. If you use this method of diffusion, run the CO2 line almost to the bottom of the tank to give the CO2 bubbles maximum time to disperse in the water.