Model Number : CO2 indicator SolutionFeatures: Made of high quality of materials. Use with CO2 indicator. Easy to use and convenient to detect concentration of CO2. Suitable for all kinds of fish tank. A wonderful solution for feeding fish and observing their living condition. Different color of liquid represents different concentration of CO2. BLUE means that CO2's concentration is too low. GREEN means it is normal. YELLOW means that CO2's concentration is too high so that it is harm to fish. Specification: Type: Liquid Color: As pictures Height: 7.7cm Net Weight: 15ml Quantity: 1 Pc Package includes: 1 x CO2 indicator Solution Notes: 1. Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you! 2. Please allow 1-3cm measuring deviation due to manual measurement.