I'm guessing a baby mangrove.

You need to do some serious research. There is a lot of information on the web. Just don't believe anything that tells you an aquarium is okay for ANY sized varanid.

Your enclosure is not large enough.
Your mulch is not deep enough.
Your hot side is not hot enough.
Your water container is not roomy enough. (I haven't seen pics, but if it's in a 20 gal. aquarium, then I am correct).

Chris