In addition to regular feeding with essential nutrients and trace elements, plants require a plentiful supply of carbon dioxide (CO2) during daylight hours to photosynthesize and grow. In a well-planted aquarium CO2 is in great demand and if not added regularly will become the most dominant factor limiting plant growth.
While CO2 is essential for plants, too much CO2 can reduce the pH of the aquarium water to levels that are stressful for fish and therefore CO2 should be monitored at all times. CO2 systems can be automated to maintain a preset pH in the aquarium or can be switched off at night when the photosynthesis process is reversed and plants actually release some CO2 into the water.
Underwater Ecosystems offers both the individual components and complete kits required for dissolving CO2 in planted aquariums.