DYI CO2 generator and cloudy aquarium

Hello all.

I decided to try a DIY CO2 generator (soda bottle, yeast, sugar) in my
aquarium (about 63 gal). I used a valve preventing aquarium water siphoning
into the bottle. What about the other way round? How can I prevent yeast
mixture from getting into aquarium?

Couple of days ago the aquarium became very cloudy. I suspect the contents
of the generator somehow made its way to aquarium, although the level in the
bottle remained unchanged. How can I check if some yeast really got into
aquarium? What are other possible reasons of cloudiness?

TIA