my friends and i run a dance club and we have a large fog machine. IT DOES NOT RUN ON WATER!
the fog is caused by using a fog solution, it has a specific smell. doesn't small bad IMO, but has many chemicals that would be very unhealthy for a fish.
just picture this, if all it fogged out was water, it would be steam, which would eventuially condense and make big wet puddles in your room where tha fish are. this would happen in clubs too and no one wants to swima nd plash, they want to dance.
the way to counter this is by adding certain chemicals that evaporate quickly. one such chemical is acetone and other alcohols. that is why if you leave a bottle of nail polish remover (essentially diluted acetone) will evaporate.
ok that explanation was longer than i thought. so in summary, no don't get this it will either kill or badly injure your fish. won't be all that great for your health too if kept running a lot.