I have a large red zebra that has started to isolate himself from the rest of the tank. He normally swam with the rest of the tank, usually pretty active an agressive, voracious eater.
Lately he tends to spend a lot of time in and around a cave I have set up. He comes out and swims around the area of the cave, then goes back in. Often stands gaurd at the opening to the cave. He seems indifferent to food - he'll eat a little here and there, but nothing substantial and not aggressively eating. He's not lethargic, but he just seems lazy and "bored" with the whole fish life.
Any thoughts?
(yes, I know I'm humanizing his behavior, but I can't think of any other way to describe it.)