>>I bet he will butch up and grow to like the extra space.

That's the problem though I think, he has a deeper tank now but less floor space. His Rubbermaid is an under the bed storage box that is very very wide, so he has a lot of floor space in that, but it's shallow.
He's not eating either, I'm stressing him out too much I fear.
:::sigh:::
If it comes down to moving him back, I do have a use for this larger tank. I had hermit crabs dumped on me in 2001, they've grown a lot, from quarter size to a bit bigger than golf ball size now. They could always use a larger tank than the 20 long they live in.
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PHRatz