My Aro's have always been scared in the dark. I use a clip on desk light on the ends at night. I don't dare make my tank all dark at night, or my Aro bumps and splashes and hurts himself. I choose the amber color flame shaped bulb, it's a real mellow light, but it makes all the difference in the world. They also add a little heat, both on at night can at 1/2 a degree of heat.