I was curious if anyone else here has measured their rate of CO2 flow in a standard unit of measurement. (ie. Not "bubbles" per second.) Knowing this would allow you to search for a rotameter / flow-meter to use in place of the common & woefully inadequate bubble counter.
It's easy to do. I used a glass measuring cup but a graduated cylinder or any container of a known volume will work. Submerge the cup in a bucket of water and invert. As long as the rim of the glass stays below the surface of the water in the bucket you can raise most of the glass (bottom-up) out of the water and the glass will remain full of water. With your CO2 feed line disconnected from your aquarium put the end of the tube in the bucket so the bubbles flow into the glass displacing the water. Time how long it takes for the glass to fill with CO2 gas & you'll have your measured rate of flow.
It's easy to do. I used a glass measuring cup but a graduated cylinder or any container of a known volume will work. Submerge the cup in a bucket of water and invert. As long as the rim of the glass stays below the surface of the water in the bucket you can raise most of the glass (bottom-up) out of the water and the glass will remain full of water. With your CO2 feed line disconnected from your aquarium put the end of the tube in the bucket so the bubbles flow into the glass displacing the water. Time how long it takes for the glass to fill with CO2 gas & you'll have your measured rate of flow.