I was shopping for a back splash for the aquarium, and I happened upon this really neat shimmery blue poster board. It looked like tin foil that had been colored with a blue marker.

However, it does have a slightly reflective surface and the rainbow shark found its reflection this morning and looks like it is attacking the back glass of the tank.

Is this harmful to my fish, do I need to change that out, or should I leave it alone and let him figure it out?