I had my scape set up without water for a bit and all the driftwood that was buried by the substrate started growing some light green mold or fungus? Probably because it was moist under the substrate, but would it be safe to add fish or shrimp to it?
It's most likely safe, but without knowing what type of mold it is, it would be impossible to know. But the odds are definitely in your favor. A better chance of it becoming shrimp food than it killing the shrimp i suppose.