Need some input on this problem. I have a 30 gallon with a piece of mopani wood in it. Last week I emptied the tank of fish and it had set fishless for 3-4 days. I then noticed a fuzzy buildup of this slime on the wood. I took it out to clean it off and man what a stench!I replaced the wood back in the tank and before going to purchase more fish yesterday, I noticed it was back again! Anyone have an idea what I can do?