My mom thought I was nuts at first for taking Simon home, not believing that this "ugly gray homeless fish" would become colorful like I said he would. But he didn't even take a week to go bright red!
All it really took was clean water. In fact, we had to stop at Fareway on the way home, so I replaced half his cup water with bottled drinking water in the car. When we came out, his color had already spread more into his fins. Poor dude just didn't want to be swimming in ammonia.
That first pic is on my desk at home, by the way. That was after I'd replaced half the water. I don't have a good pic of him in the store, but he was worse.
Of course, good food and lots of plants to hide in didn't hurt! :P