Any change in the tank will likely stress them out. Same thing happened with me. I switched his bedding from wood chips to aspen. He hated it. He didn't go to bed, and was out and about. His regular schedule was thrown off. So I switched it back.

You can leave it as is, and he'll get use to it, or you can switch it back. Try putting a towel or blanket over the cage in the mean time. That usually works for me, when I know its his regular bed time, and he isn't going to sleep. It just lets him feel more secure.