• The UP Bubble Counter & Check Valve D-512 is a must have for any tank with CO2 injection.
•  A bubble counter allows the user to estimate the CO2 injection rate by counting how many bubbles pass through the counter per minute.
• Mountable both inside and outside the tank, this is a modern, small and unobtrusive bubble counter. 
• Easy to read and easy to maintain. 
• A check valve prevents water from your aquarium from siphoning back into fragile and expensive CO2 equipment such as regulators and solenoids. 
• Mountable both inside and outside the tank, this is a modern, small and unobtrusive check valve.
•  A wise investment to protect your equipment from damage - at such an affordable price, there is no reason not to get one To use, 
• fill the bubble counter with water, or if you prefer a bright coloured solution to make it easier to read. 

The easiest way to do this is to attach a small piece of tubing to one end, and then use a syringe to force water down the tubing and into the bubble count. Then, simply connect the bubble counter in-line from your regulator to your diffuser. When the regulator is open, you will be able to calculate your CO2 injection rate by counting how many bubbles pass through the counter per minute. Using a check valve couldn't be simpler, simply mount inline from your regulator to your diffuser, ensuring that the narrower end is facing down. If you are using other accessories such as bubble counters, then insure that the check valve is the last accessory before the solenoid/regulator