CO2 Calculator

📖 About this CO2 Calculator

This tool estimates dissolved CO2 in your aquarium based on pH, KH, and temperature (depends on the method). It’ll also help you understand if your CO2 level is in optimal range for your fish, shrimp, or plants.

⚠️ Why different methods give different results

You can choose between several calculation methods. The “Simple” method (fixed pKa=7) is common in most online calculators.

The temperature‑compensated and Millero‑based methods are considered to be (in science) more accurate for freshwater or marine tanks. However, they are way more complex for our simple tanks.

Therefore, depending on the method, the same pH and KH can give VERY different CO2 readings. For example, 2 dKH and pH 7.0 can show 6 ppm with the simple method, but only 1.5 ppm with temperature compensation. Always check which method matches your experience.

🐟 Real aquarium factors matter

Always keep in mind – No calculator can replace your own eyes and test kits.

CO2 levels also depend on surface agitation, plants consumption, water flow, and even atmospheric pressure. Use this calculator as a guide – not as an absolute truth. Watch your fish and shrimp behaviour, and adjust accordingly.

🔧 How to use it effectively

Start with the “Simple” method to compare with other online calculators. Then try the “Temperature compensated” or “Millero freshwater” for a more science‑based estimate. The color‑coded chart helps you see safe pH/KH combinations for your tank type. Share your settings with others using the “Share” button.

Remember: Every aquarium is unique. What works for one tank may be dangerous for another.