So, now about 10-days since my original SOS...
Photo shows where he seems to have settled in...showed up 1-day after the post that he was missing. He's located in a cave-like recess (see inside red circle) and has shaded himself some from the direct T5s.
Have been in communication with some folks who have had success with nems and they are positive about me keeping him even though I am inclined to put him up for adoption to a good home.
He looks healthy and seems to be thriving in his current home. Not really sure I understand the cautions of those who feel a tank needs to be older...unless the concern is about stability of the system...which makes sense as I understand that nems can be like the 'canary in the coalmine' sensitivity wise.