Seachem CO2 Indicator Solution – At-a-Glance CO2 Monitoring for Planted Tanks

See Your Tank's CO2 Level at a Glance

Dialing in CO2 for a planted tank is guesswork without a live readout, and too little starves your plants while too much stresses your fish. You need a simple, ongoing way to know where your CO2 sits.

Seachem CO2 Indicator Solution works with the Seachem Glass pH Checker to change color with the pH of your aquarium, giving you an easy, effective, continuous check on CO2. A yellow color indicates lower pH and more CO2; blue indicates higher pH and less CO2; green sits in between.

The indicator comes from Seachem Laboratories, the chemistry-driven company founded in 1979 in Madison, Georgia and staffed by in-house chemists. That in-house chemistry expertise is exactly what you want behind a solution whose job is to read your water's pH and translate it into a clear, continuous CO2 signal.

1. Holding the funnel side up, fill the small bulb with 20 drops of indicator solution.
2. Turn the funnel down without spilling and insert the checker into the aquarium, trapping air in the funnel.
3. Attach it far from any diffuser and read the color: yellow (more CO2), green, or blue (less CO2).

Take the guesswork out of CO2 dosing. Add to cart.

What It Does

For use with the Seachem Glass pH Checker. The indicator solution changes color according to changes in the pH of the aquarium, providing an easy and effective way to check for CO2. Yellow indicates lower pH / more CO2; blue indicates higher pH / less CO2.

Directions

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

Available Sizes

50 mL

Why Seachem CO2 Indicator Solution

• Continuous readout: it gives an easy, effective, ongoing check on CO2 rather than a one-off snapshot.
• Clear color signal: yellow means lower pH and more CO2, blue means higher pH and less CO2, and green sits in between.
• Simple to run: 20 drops in the checker bulb and correct placement are all it takes to start reading.
• Pairs with the Glass pH Checker: designed for use with the Seachem Glass pH Checker for accurate placement in the tank.

Best For

Planted aquariums running injected CO2, where you want an at-a-glance way to keep levels in the healthy range for plants without stressing fish. Useful for both dialing in a new system and monitoring an established one.

FAQ

How much solution do I use? Fill the small bulb of the pH Checker with 20 drops of indicator solution, following the directions.

Where should I place the checker? Attach the pH Checker at the furthest point from any diffuser so the reading reflects the tank rather than the diffuser output.

What do the colors mean? Yellow indicates lower pH and more CO2, blue indicates higher pH and less CO2, and green sits in between.