hey i had the same stuff in mine... i asked in kingsnake and got a ton of responses-most of which said the humidity was to high, but mine was at 80, and most said it was harmless. i moved my log to actually half in/hlaf out of the water after wiping the mold off and it hasnt come back. i dont think its dangerous and like another guy told me it is very sporadic in its growth patterns. kinda adds something natural to, but you might want to get it off i guess, just in case