Good looking monitor.
Only thing I have a problem with is his current enclosure...
You should deffinatly get him out of the fish tank fast, and into a made enclosure plywood melamine etc. and one without a screen top.
As you probably dont see problems now, but will so in the future when he starts growing.
And also get him off that bark substrate and throw him on some natural soil/dirt with a little sand mixture.
Also just curious how much and how many times a week do you feed him, also with what?