As an update. After I cleaned and set it up, I moved him again to the same tank he mysteriously appeared in a few days ago. He just molted last night, so I think he is gonna be perfectly fine. But with a name like Chuck Norris, he will never die.
Best freebie ever. He is slowly starting to get more curious, and follows my other smaller cleaner everywhere. Even cleaned my hand 2 days ago with the other cleaner.