The Dymax CO2 Drop Checker (also sold as the Dymax Crystal CO2 Indicator) is a glass monitoring tool for planted aquariums. It tracks dissolved carbon dioxide and pH levels through gas exchange inside an air pocket. The indicator liquid changes colour to show if CO2 output is too low, safe, or dangerous.

How to Use:

• Fill the unit: Turn the glass drop checker sideways or upside down. Add about 5 to 15 drops of indicator solution into the bulb (indicator solution is usually sold separately).
• Position it: Attach the suction cup. Place the drop checker underwater near the middle or lower section of your tank, away from surface agitation or direct heater flow.
• Wait for results: Allow 1 to 2 hours for the gas to react and change the liquid colour.

Reading the Colours:

• Blue: CO2 level is too low. Plants may lack fuel to grow well.
• Green (or light green): CO2 level is safe and ideal (around 30 ppm).
• Yellow: CO2 level is too high. This can harm or suffocate your fish. Lower your bubble count.