On my planted tank I used 20% limo black window tint on the two sides and back. One piece, just started at one side and installed it around to the other side. You can see through the sides, but when looking through the front glass, you cannot see through the back. Also cuts down on any stray sunlight into the tank and at night the 3.5 wpg only shines out the front of the tank instead of lighting the whole room.