The Dual and Single CO2 Drop Checker Kits by Glosso Factory is used to measure CO2 levels in planted aquariums and fish tanks with live plants.  The kits work by changing color as CO2 levels rise and fall.  Too much dissolved CO2 can be harmful for fish and livestock.  With this kit aquarists can accurately measure optimal CO2 levels that promote plant growth while helping to keep fish safe.  

Green color indicates between 25-30 ppm (for 4.2 dKH solution) (and 50-60 ppm  for 8.4 dKH) levels ideal for plant growth

Blue color indicates lower levels of CO2; CO2 injection can be increased gradually until the indicator solution turns green.

Yellow indicates high levels of CO2 that can be harmful to livestock, if the solution is yellow lower the CO2 injection and check the solution every few hours until the color is green.

4.2 dKH measures normal and low range CO2 levels.

8.4 dKH measures higher levels of CO2

By keeping both drop checkers near green at all times, aquarists that typically maintain higher dissolved CO2 levels can ensure greater accuracy in measurement. Further, dual drop checkers will provide a check on each other for additional measurement reliability.