When should I turn on and off the CO2 in my aquarium?

Plants use CO₂ when there is light to photosynthesize. However, the process reverses at night and becomes the respiration cycle, in which plants consume oxygen and sugars and release CO₂. Therefore, we want to shut off the CO₂ regulator when the aquarium light is off. For more optimized CO₂ usage, program the regulator’s timer to turn on 1–2 hours before the light comes on and turn off 1 hour before the light shuts off. (If you only have one timer, you can use the same timer with a power strip so that the light and regulator turn on and off at the same time.)

For more information on CO₂ systems in high tech planted tanks, read the full article.