Ornate monitor enclosure question

[Grendel]

So today I measured my monitor again and he is now 16 inches, he was 15 when I originally posted 11/22/12.
I half buried a round piece of bark open at both ends and that's now his favorite hiding spot. Substrate is sand dirt mix with leaf litter/pine straw on top.

[Grendel]

Here are some pictures of him.

[Grendel]

Close up of head/ behind him are stacked bark pieces, with a black light directly above them for heating of the stack.

[Grendel]

One more body shot. Sorry these loaded sideways, not sure what's with that, must be because I used my phone.

[Pirarucu]

He sure is a pretty one. Strange how that one row of spots cuts off instead of going all the way across.
How much is he eating?