FIRST....... how are you regulating your heat source? I know what you posted in your first post on this thread and I am on my phone so I am not going to try and find the others this second.
That photo sure looks like you have a burn going on. Clean the tank, remove all the substrate, regulate your heat source and use paper towels.
When I get to my PC I will merge all the multiple threads together.
For future reference, it doesn't help you or anyone else to keep making a new thread on the same subject.
I just realized way back I had already tried to tell you that you would need a thermostat.