He pooped this morning after I got in - nice and orange! I'm glad he waited until I got here, so he didn't have it in his cup overnight.
The water tested fine - they said the pH was 7.0, and everything was in the safe level, including amonia at .5 (not zero unfortunately). The only thing was the water was "hard," but he said that could have been from the Epsom Salt.
I just let him out of his cup, and he's swimming like a champ at the top of the tank!
I have to leave early today to attend a memorial, so I wanted to check him out for awhile before I leave (in case I have to put him back in the cup) - so far, so good.
Since the water checked out OK, I may hold off on changing it today. How often should I change it anyway? I'm so glad I didn't give up on him - thanks so much for your encouragement and for contacting Sakura8 for me on Sunday!
P.S. He's still at the top!