The AquaPro Glass CO2 Drop Checker Kit is a complete monitoring tool for planted aquariums that comes with a glass drop checker, a suction cup, and a pre-mixed 15ml 4 dKH indicator solution.

What’s Included in the Kit:

• Glass Drop Checker: A transparent glass reservoir designed to house the indicator fluid.
• Suction Cup: For securely mounting the drop checker to the inside wall of your aquarium.
• CO2 Indicator Solution: Pre-mixed 4 dKH (carbonate hardness) solution with built-in pH indicator dye (no mixing or math required).

How to Set It Up:

• Fill the Reservoir: Turn the drop checker upside down and fill the bulb approximately halfway to 2/3 full with the pre-mixed AquaPro indicator solution (using a small pipette or syringe helps avoid spills).
• Invert & Mount: Turn the drop checker right-side up so an air pocket is trapped inside the bulb. Attach it to the inside glass of your aquarium using the suction cup.
• Positioning Tip: Place it away from your CO2 diffuser (ideally on the opposite side of the tank) so it measures general water circulation rather than direct, un-dissolved CO2 bubbles.
• Wait for the Reaction: Dissolved CO2 outgasses from the tank water into the air pocket inside the checker and changes the color of the liquid. Allow 1 to 2 hours (sometimes up to 3 hours) for an accurate color reading.

How to Read the Colours:

• Blue: CO2 level is too low (increase your bubble rate or check distribution).
• Green / Deep Green: CO2 level is optimal and safe for plants and fish.
• Yellow: CO2 level is too high and dangerous for fish/livestock (reduce CO2 injection immediately).

Maintenance Tips:

• Refresh the Solution: Replace the indicator solution inside the drop checker once a month (or every 2 to 3 months depending on algae growth and clarity) to keep readings accurate.
• Do Not Use Tank Water: Always use a dedicated 4 dKH reference solution rather than straight aquarium or tap water, as mineral content in tank water distorts pH/CO2 readings.