Originally Posted by Horsegirlmaddy
I have a fairly heavily stocked tank with a heavy duty cannister filter, but it's a hexagonal tank so the surface area for gas exchange is less than a long or wide tank. I run an air pump and air curtain (as opposed to an air store) for maybe 6 hours a day or less, and it seems to really make a difference in oxygen content. But that's just my opinion. I use a fluval air pump for up to 100 gallons on my 60 gallon
Small bubbles from whatever source you have in your tank, don't create sufficient water movement at the surface, even a lot of small bubbles won't make a significant difference in the amount of oxygen that mixes with the water and the amount of carbon dioxide that's released.
The key to good gas exchange is to really agitate the water at the surface. If you use an air pump, then simply attach a length of tubing, without the air stone and place it at the bottom of the tank. You'll create large bubbles. When those much larger bubbles reach the surface they'll churn up the water much more and then you get good O2
content in the tank water and CO2
released into the air.