Has anybody tried setting up a system where the outgassing of a fermenting liquid (kombucha, beer, mead, etc.) is used in an aquarium to supplement it with CO2?
I did it for awhile in a low tech set-up. I had a powerhead in the tank, and ran tubing from my wine fermentor into the top of the powerhead to disperse the bubbles. It was fine during the initial 5-7 days of ferment, when things were really going fast, but the ferment eventually slows down and bubbles become sparse (just the nature of fermentation). So, if you were really relying on it, you'd probably be disappointed, and even have negative results, because you won't reasonably be able to provide consistency. But if you aren't relying on CO2 in the fist place, it makes for a decent "boost" for a couple days.
A word of warning: make sure you have enough head space in your fermentor to avoid the must (or any solids in it) from foaming up and into your tubing. If this happens, one of 2 things will result:
-You will get must (of the wine/beer/whatever) in your tank, and it will mess things up in a hurry;
-Your airline will clog and your fermentor will become a bomb...and you may end up with splattered wine all over the living room, ceiling, walls, carpet....a lesson I learned the hard way.