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CO2 Dosing Calculator
Calculate the right CO2 bubble rate for your planted tank. Optionally enter pH and KH to check your current CO2 level.
Tank Volume (Gallons)
Plant Density
Lighting Level
Current Water Parameters (Optional)
Enter your current pH and KH to check your existing CO2 level.
Frequently Asked Questions
How much CO2 does a planted tank need?
Most planted tanks benefit from 20-30 ppm (parts per million) of dissolved CO2. Low-tech tanks with undemanding plants can thrive without supplemental CO2, while high-tech setups with demanding carpeting plants and high light need consistent CO2 at 25-30 ppm throughout the photoperiod.
What happens if I add too much CO2 to my aquarium?
Excess CO2 (above 35 ppm) can suffocate fish and shrimp by lowering oxygen levels and making the water too acidic. Signs of overdosing include fish gasping at the surface, rapid gill movement, and lethargy. Always use a drop checker (should show green, not yellow) and turn off CO2 at night when plants are not photosynthesizing.
What is a drop checker and what color should it be?
A drop checker is a small glass device filled with indicator solution that changes color based on CO2 levels. Blue means too little CO2, green means the ideal range (20-30 ppm), and yellow means too much CO2. Place it at mid-tank height on the opposite side from the CO2 diffuser.
Are there alternatives to pressurized CO2 injection?
Yes. Liquid carbon (like Seachem Excel or Easy Carbo) provides a small CO2 boost but is much less effective than gas injection. DIY citric acid and baking soda reactors are cheaper but inconsistent. For low-tech tanks, choosing CO2-tolerant plants and limiting light can eliminate the need for supplemental CO2 entirely.
When should I turn my CO2 on and off?
Turn CO2 on 1-2 hours before your lights come on so levels build up, and turn it off 1 hour before lights go off. Plants only use CO2 during photosynthesis (when lights are on). Running CO2 at night wastes gas and can dangerously lower pH and oxygen while fish sleep.