Mold in Fire Bellied Toad tank

[FireTigress]

My setup for my fbt is growing mold. I have a small log separating the land, which is peat moss and aquarium gravel, and the water. I was gone for about four days and my sister was feeding the toads, when I got back, there was white mold growing on and around the log. Should I take the log out for good or should I clean it and put it back? Should I change the substrate? I also have a live plant on the land side. The kind used in those vase tanks for beta fish. What other kind of setups look good and work well for the toads. These guys are my first amphibians so I don't have alot of experiance to work with. Thanks.