CO2 is one of the key elements for plant growth. Insufficient CO2 will result in improper growth of aquatic plants. On the other hand over; supply of CO2 is dangerous to fish and other aquatic life. Therefore it is important to constantly monitor CO2 to ensure the correct amount is supplied into the planted aquarium. Use of a bubble counter can only predict the amount of CO2 by counting the releasing bubbles from the CO2 supply. The Dymax CO2 Crystal Indicator is a device that works with the indicating solution to provide accurate reading of CO2 dissolved in water. With this device monitoring of CO2 content is more efficient and accurate.