Legend Co2 Drop Checker & Legend Indicator Solution


Legend CO2 drop checker made of high-quality glass, use to measure CO2 levels at a glance(including Indicator solution).
Apply to fish tank, aquarium, especially aquatic plants, tropical fish to watch and cultivate for fish tank.
Monitor to be installed below the water surface about 10cm, it is recommended not to install too far from the refiner.
You need to be very careful about the health of your plants and carbon dioxide is one of their major requirements.
This CO2 monitor is one of the most vital items of your aquarium kit that helps you to keep a constant check on CO2 levels in the water.


1 x Legend CO₂ Checker with suction cup

1 x 15 ml indicator solution


The permanent test is filled with 1 – 2 ml of the Legend CO2 indicator solution and then positioned in a well-circulated area in the aquarium. After about 1 – 2 hours, the CO2 content of the aquarium water can be read. A green colour indicates an optimal CO2 supply of approximately  30 mg/l.


A Legend CO2 indicator solution is very useful in an aquarium. Often, aquatic plants lack the essential CO2, preventing optimal growth. With a CO2 permanent test, the CO2 level can be controlled with sufficient accuracy. The dye bromothymol blue used has the property of changing colour in a defined pH range.

CO2 diffuses from the aquarium water through the air bubble in the permanent test into the test solution and vice versa. Depending on its CO2 content, the pH value of the test liquid and thus its colour changes. A defined carbonate hardness in the test liquid determines at which CO2 concentration a certain pH value is established. The Legend CO2 indicator solution turns light green when the pH value is around 6,6. This is achieved at a CO2 concentration of 30 mg/l. For this reason, the Legend CO2 indicator solution indicates a light green tone at a CO2 value of the aquarium water of  30 mg/l. If the CO2 supply in the aquarium is less than  30 mg per litre, the test reagent remains blue; if the CO2 supply exceeds the mark of 30 mg per litre, the test reagent turns yellow.


pH Checker Solution SDS 20210729.pdf


Storage: at room temperature. Protect from frost and heat. Keep out of reach of children and pets.

Use: For fertilization of ornamental plants in an aquarium only.
See the pack for detailed dosage recommendations. Note: Official guidance recommendations take precedence.


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Made of high-quality glass

Visually very appealing

Good to read

The necessary suction cups are included

15mL Indicator Solution is included