I think the mold/fungus you are seeing is more likely to be spread by water splashing than airborne spores.
You may want to try something like a swimming pool algicide - it's a quarternary ammonium compound, also seen in products like Physan and Consan. Try watering a FEW pots of plants you aren't too attached to, to check for phytotoxicity. I'd use a dose in the ball park of 1/2 teaspoon per gallon of water. Or better yet, repot some plants, put the old medium back in some other pots, and experiment on that.
(For what it's worth, I use 1/4 tsp per US gallon when making up a stock fertilizer solution, as I was getting some kind of bacterial growth. Probably something in my water storage tank. It doesn't seem to harm any of my plants once diluted out, at rate of 1 oz/US gallon.)