So my friend just bought a used tank without looking at it first... yes she is kicking herself now for it, but that aside... there is something weird going on with the black silicone in two of the bottom inside corners the are a copper color. It's only about the first inch of silicone from the bottom of tank, but what in the world would cause that? I've never seen something so weird. And it is the silicone itself that changed not just something on the surface.... I meant to get a picture I will still try. Thanks guys.