CO₂ Bubble Rate & Dosing Calculator.

This calculator uses the common aquarium estimate CO2 (ppm) = 3.0 × dKH × 10^(7 − pH). The estimate assumes carbonate hardness is the main buffer affecting the pH relationship. Other acids, buffers, tannins, or pH-adjusting products can make the result less reliable, so treat it as an estimate rather than a laboratory measurement.

Around 20–30 ppm is a commonly used range for many planted aquariums. About 30 ppm is often used as a reference point for higher-light planted setups, while low-tech aquariums can grow successfully at lower concentrations. The appropriate level depends on plants, lighting, circulation, and livestock.

30 ppm is a commonly used target for many CO2-injected planted aquariums, but it is not a universal requirement. Some aquariums perform well below 30 ppm, while pushing CO2 higher does not automatically produce better results. Livestock behavior and reliable measurement should be considered alongside plant growth.

Bubble size varies substantially between diffusers, regulators, and bubble counters, so bubbles per second is only a starting reference. This calculator estimates a starting rate from tank volume using approximately 1 bubble per second for every 12 US gallons. Adjust the injection rate gradually while monitoring CO2 levels and livestock.

Tank volume is the main input used by this calculator's starting bubble-rate estimate. It calculates approximately one bubble per second for every 12 US gallons. Actual CO2 requirements can differ because diffuser efficiency, surface agitation, circulation, plant mass, lighting, and bubble size vary between aquariums.

The pH-and-dKH estimate assumes carbonate alkalinity is the main factor affecting the pH relationship. Other buffers, tannins, phosphate-based products, and acids can interfere with that assumption. For a more useful cross-check, many aquarists use a drop checker with a known 4 dKH reference solution.

The pH drop method compares the aquarium's running pH with the pH of water after it has been allowed to lose most of its dissolved CO2. A larger pH difference generally indicates more dissolved CO2. The method works best when carbonate alkalinity is the main buffer and the baseline sample has been properly degassed.

The required pH change depends on your current CO2 concentration. This calculator uses the pH/dKH relationship to estimate how far the pH would need to move to reach 30 ppm while keeping dKH constant. If the calculated CO2 is already close to 30 ppm, the displayed change will be small.

BPS means bubbles per second. It describes how frequently bubbles pass through a bubble counter and is commonly used as a rough way to describe CO2 injection rate. Because bubble size and diffuser efficiency vary, BPS should not be treated as a universal measurement of dissolved CO2.

BPM means bubbles per minute. This calculator converts its estimated bubbles-per-second starting rate into bubbles per minute by multiplying BPS by 60. It is simply another way to express bubble-counter frequency, not a direct measurement of dissolved CO2.

CO2 injection is commonly reduced or stopped during the dark period because plants do not photosynthesize without light. Many pressurized CO2 systems use a solenoid and timer to start injection before the lights come on and stop it before or around lights-off. The exact schedule depends on the aquarium and how quickly it reaches the desired CO2 level.

Yes. Excessive dissolved CO2 can reduce the amount of oxygen available to fish and other aquatic animals and can cause visible stress. This calculator flags concentrations above 35 ppm as a high-risk range, but livestock response varies. If fish show signs of distress, increase gas exchange and reduce CO2 injection rather than relying only on the calculated value.

CO2 can be used successfully in aquariums containing fish and shrimp when the concentration is controlled and gas exchange is adequate. The important consideration is the actual dissolved CO2 level rather than a particular bubble rate. Introduce changes gradually and monitor livestock for signs of stress.

The two methods measure or estimate CO2 differently. The pH-and-dKH calculation depends on the assumption that carbonate hardness is the primary buffer, while a drop checker responds to CO2 diffusing into its reference solution. Differences can result from inaccurate dKH or pH measurements, non-carbonate buffers, incorrect drop-checker solution, or normal measurement limitations.

30 ppm is a commonly used reference target, so a calculated value above it does not automatically mean the aquarium is unsafe. However, higher CO2 concentrations increase the need to monitor livestock and gas exchange. This calculator labels values above 30 ppm as being above its target range and values above 35 ppm as a high-risk range.