Well, I left for an overnight trip, and apparently my heater was not turned up high enough, because my fishies' water was really cold when I got back.
And my dear beautiful Elijah was dead. I'm convinced it was not either the cold or the constipation but a combination of the two that killed him, he was already under stress and the cold water was just too much to take.
On a happier note, while I was away I picked up a beautiful blue veiltale male, Toby. He seems to have quite a personality and will be a good match for Noel once everything's settled down.