For plants, carbon dioxide is the best fertilizer available. Plants need carbon dioxide to complete photosynthesis. They extract carbon dioxide from their environment and use the energy from sunlight to turn it into proteins and sugars. With out carbon dioxide, plants would simply die off. When you add extra carbon dioxide to the environment your plants live in, they will begin to grow stronger and healthier shoots, flowers and produce. The plants' root systems will even become more expansive.
Light the candle with a match. Hold the nail's head with a rag, and place the tip of the nail into the flame. Hold it there for 30 seconds.
Push the heated nail into the center of your two liter's bottle cap. Wiggle the nail until the hole is as large as the fish tank tubing.
Push the fish tank tubing through the hole in the bottle cap so 1 inch of tubing is below the bottle cap.
Super glue the tubing in place on the top of the bottle cap. Let it dry for one minute.
Place the funnel in the mouth of the 2-liter bottle. Pour ¾ cup of sugar and 1 tsp. of dried yeast into the bottle. Fill the bottle ¾ full with water.
Place your thumb over the mouth of the bottle. Shake it vigorously for 30 seconds. The mixture will start to slowly bubble. Replace the bottle cap with the fish tubing to the top of the 2-liter.
Aim the loose end of the fish tank tubing towards your plants. Carbon dioxide will flow from the bottle, through the tubing, to your plants.
Repeat steps 5 through 7 when the mixture in the bottle no longer bubbles. Typically, the mixture will stop bubbling within one to two weeks.