CO2 Calculator
Estimate CO2 levels from pH and KH, and target bubble rates.
How it works
Dissolved CO2 (ppm) ≈ 3 × KH × 10^(7 − pH). Aim for 20-30 ppm for planted tanks. Bubble rate is tank-specific; start around 1 bubble/second per 100 L and tune using a drop checker (green = good).
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Formula & Method
Dissolved CO2 (ppm) ≈ 3 × KH × 10^(7 − pH). Aim for 20-30 ppm for planted tanks. Bubble rate is tank-specific; start around 1 bubble/second per 100 L and tune using a drop checker (green = good).
Example Calculation
At pH 6.8 and KH 4: CO2 ≈ 3 × 4 × 10^(7−6.8) = 12 × 10^0.2 ≈ 19 ppm — slightly low, so increase injection toward 25 ppm.
Frequently Asked Questions
How much CO2 do planted tanks need?
20-30 ppm is the sweet spot for growth without harming fish. Use a drop checker and watch fish behaviour.
Is CO2 dangerous to fish?
Excess CO2 (above ~30 ppm) can suffocate fish. Increase gradually, add surface agitation at night, and turn CO2 off when lights are off.