Do it Yourself CO2 Regulator

CO₂ regulator systems often cost more than $200, which is a hefty price to pay for a college student. I have a 30-gallon aquarium that is heavily planted, and I would like the plants to grow faster and with less algae and brown spots. Because plants absorb the CO₂ in the water to grow, adding more CO₂ should fix that problem. So, I’ve decided to attempt to make a CO₂ regulator that uses yeast, sugar, and a liter bottle to regulate the CO₂.

Materials

Total Cost: $20.00-$25.00

• 1-liter bottle
• Aquarium grade silicone
• CO₂ airline tubing*
• An air diffuser
• 1-2 suction cups
• Scissors
• An aquarium with live plants
• Optional: a check valve or bubble counter

*Normal airline tubing can be used, but the CO₂ type decomposes slower and has minimal leakage

Instructions

STEP 1: MAKE A HOLE IN CAP

Make a hole in the center of your bottle cap that is just a tad bit smaller than your tubing. You can use scissors, a nail, or a drill to do so.

STEP 2: TRIM TUBING

On one end of your airline tubing, make a slanted cut. This will make it easier to fit the tubing through the bottle cap.

STEP 3: THREAD TUBING THROUGH CAP

Thread the slanted end of the airline tubing 1.5-2” into the cap with the longer side being on the top part of the cap.

STEP 4: SEAL TUBING

Seal the tube and the cap together using aquarium grade silicone. I also put silicone inside the cap, as well. This allows no air or CO₂ to escape from the system once it is up and running. It can take up to 48 hours for the silicone to become fully sealed.

STEP 5: ADD BUBBLE COUNTER OR CHECK VALVE

At this point, you have a few options. You can either add a bubble counter, a check valve, or neither. In the final product, you can see that I’ve added a bubble counter which minimizes the amount of yeast that enters the tank. Before I added it, the water would get a bit cloudy around the diffuser, and the tubes would get clogged and need to be cleaned. Now, the yeast falls to the bottom of the bubble counter and only the CO₂ continues on to the fish tank. On the other hand, a check valve basically does not allow water to flow backward through the system, but it is not required if you set the system up correctly. If you don’t mind a little yeast in your aquarium or aquarium water in your yeast system, neither of these absolutely need to be added.

STEP 6: ATTACH TO DIFFUSER

Attach the other end of the tube to an air diffuser. I also did not get a chance to photograph this step, but you can see what it looks like in the final image.

STEP 7: FILL BOTTLE

Fill the liter bottle halfway with warm water. It is important that the water is warm because it activates the yeast once it is added. However, the water also cannot be hot because hot water will kill the yeast cultures. If the water is too hot to touch, it will be too hot for the system, as well.

STEP 8: ADD SUGAR

Pour about a cup of sugar into the lukewarm water, and shake it until the sugar dissolves into the water.

STEP 9: ADD YEAST

Put one packet of yeast into your lukewarm water and gently shake the bottle to mix it, as well. The instructions called to add baking soda which apparently helps the CO₂ levels stay more constant, but I didn’t have any on hand.

 STEP 10: PLACE IN TANK

Screw the cap on with the tube and place the diffuser in your tank. It should start bubbling within a day or two and last a couple of weeks.

THE FINAL PRODUCT

For the most part, my CO₂ regulator system seemed to work perfectly. It released a steady stream of CO₂ for at least a few weeks before running out. The only downside was emptying and smelling the yeast bottle afterward. I would highly recommend this setup as a way to keep your plants nice and healthy without breaking the bank.