Its a 75G tank (48"x18x18), planted, with a planted pond at one end. Unless the pothos or fern started moving and attacking him, I dunno what was going on. There aren't any other cages visible to him (bearded dragon, not visible below)...

This might just end up being a huge unknown...

I just uncovered the cage and noticed that he regurged. Wasn't over fed by any means, so it was either caused by the stress (most likely) or some sort of bacteria/parasite load. I'd imagine that a parasite load would have not manifested itself a long time ago, and not with this type of reaction.

At the moment, he's acting much like normal. Little nervous, but closer to normal