It's definitely possible. I've done it multiple times in tanks that had plenty of surface agitation for gas exchange. The 2 most memorable times were when I setup a 1 gallon jug with a DIY yeast mixture. I placed the end of the tube in the tank w/no method of diffusion. About an hour later it was producing CO2. Went to bed. Woke up the next morning and all the panda corys were completely drunk. I thought I missed the party and then I realized it was the DIY CO2. Mind you it was a 10 gallon tank with a Sunsun 302 canister with the spraybar pointed at the surface.
The second time was when I first installed my Rex Griggs reactor with DIY CO2 on a 20g long. Within an hour of hooking up the wine bottle DIY CO2, all of the corys were drunk off of the CO2.
Both times I was really surprised, b/c I too had read that it was impossible...
Fraternity of Dirt #30 - SunSun Pimp Club #20 - Eheim Pimp Club #412