CO₂
LGND CO₂ Indicator Solution™
For use with the Legend glass pH Checker
Recommended for planted aquaria with CO2 injection systems
£ 10.99 (incl. VAT)
- EUR: 12.79€
Overview
Legend CO2 Indicator Solution™ is a ready-to-use reference solution designed for continuous monitoring of dissolved CO2 levels in planted aquariums. When used with any standard permanent CO2 checker (drop checker), the solution provides a simple visual indication of whether carbon dioxide concentrations remain within the optimal range for healthy aquatic plant growth.
Unlike direct measurements based on aquarium water chemistry, Legend CO2 Indicator Solution™ contains a precisely calibrated carbonate hardness reference solution that allows CO2 levels to be assessed independently of fluctuations caused by humic substances, tannins, buffers, or other dissolved compounds. This helps provide more reliable and consistent CO2 monitoring.
The bromothymol blue indicator changes colour according to the concentration of dissolved CO2 diffusing into the test chamber. Under normal operating conditions, a green colour indicates approximately 30 mg/L CO2, which is generally considered the ideal concentration for most planted aquariums. Blue indicates insufficient CO2 levels, while yellow suggests excessive CO2 concentrations that may stress fish and other aquarium inhabitants.
Size: 120 mL.
Directions
Fill the permanent CO2 checker with approximately 1–2 mL of Legend CO2 Indicator Solution™ and install the checker inside the aquarium in a location with moderate water circulation, away from direct CO2 injection points.
After installation, allow approximately 1–2 hours for the solution to equilibrate with the aquarium water. The colour of the indicator will gradually change according to the dissolved CO2 concentration.
Interpret the colour as follows:
Blue indicates low CO2 levels, generally below the recommended concentration for optimal plant growth.
Green indicates an optimal CO2 concentration of approximately 30 mg/L and represents the target range for most planted aquariums.
Yellow indicates elevated CO2 levels above the recommended range and may signal excessive carbon dioxide injection.
For best results, inspect the indicator daily and adjust CO2 injection rates gradually as required.
FAQ
Why use a CO2 indicator solution instead of testing aquarium water directly?
Traditional pH and KH calculations can be influenced by tannins, humic acids, buffers, and other dissolved substances. Legend CO2 Indicator Solution™ uses a calibrated reference solution, allowing CO2 levels to be assessed independently of aquarium water chemistry.
How long does the indicator take to respond?
Most installations require approximately 1–2 hours before an accurate colour reading is obtained. Response times may vary depending on water movement and CO2 stability.
What colour should I aim for?
A light to medium green colour indicates approximately 30 mg/L CO2, which is generally considered ideal for healthy plant growth in most planted aquariums.
Why is my indicator always blue?
This usually indicates insufficient CO2 injection, poor circulation around the checker, or inadequate dissolution of injected CO2 within the aquarium.
Why is the solution yellow?
A yellow colour indicates elevated CO2 concentrations. Reduce CO2 injection gradually and monitor livestock closely for signs of respiratory stress.
How often should the solution be replaced?
For maximum accuracy, replace the indicator solution every 3–4 weeks or whenever contamination, evaporation, or colour instability is observed.
Safety
For aquarium use only. Keep out of reach of children and pets. Do not ingest. Avoid contact with eyes and skin. If contact occurs, rinse thoroughly with clean water.
Do not use the solution directly as a water treatment or additive. Store tightly closed in a cool, dry place away from direct sunlight. Dispose of unused product and empty containers responsibly according to local regulations.