When I only kept a few snakes, Repti-bark was my bedding of choice. Repti-bark is heat treated and inhibits mold growth, holds moisture well, and is aesthetically pleasing. Not to mention the rough surfaces that allow for easy shedding.
I never had any king of growth or fungus on mine when I used it.
Truthsdeceit, are you sure you were using Repti-bark and not some Home Depot type of bark? The type you can buy at these type of stores is not treated like the Repti-bark and therefore will allow fungus and mold growth.