I'm new to owning tegus. I just recently (last week) got my baby black and white argentine. He's temporarily set up in a 20 gallon tank with a locking screen lid. His substrate was about 2" deep (dampened forest floor mulch) with some branches and some artificial plants. I'm using a 75 watt basking bulb and a 100 uvb bulb. Today while feeding I noticed that there's a layer of mold covering about 50% of his substrate. I've replaced the mulch and it's now about 4-5" deep. What can I do to prevent this?? Any other advice for a new tegu owner would be appreciated also!