The Seachem CO2 Indicator Solution 50 ml Refill for pH Checker is for use with the Seachem pH Checker. This indicator solution changes color according to changes in the pH of the aquarium as a result of CO2 gas. The pH checker makes monitoring CO2 concentrations and pH level in planted aquaria easy.

Directions:
Holding the funnel side of pH Checker upward, fill the small bulb with 20 drops of indicator solution. Slowly turn the funnel side down avoiding any spillage of the solution. Insert pH Checker into aquarium funnel side down, trapping air in the funnel. Attach the pH Checker in aquarium at the furthest point from any diffuser.The color of the indicator solution will change yellow to green to blue according to the pH of the water. A more yellow color indicates lower pH / more CO2. A bluer color indicates higher pH / less CO2.