whats is the effect of putting lights on top of the tank?
A. Can stress out your bichirs if left for way to long. They will develop skittishness. May not also eat.
does it makes the color of your bichirs lighter?
A. My bichirs gets pale when the lights are off but that doesn't mean they are stress. They are just blending in. They later goes back to normal in the morning to match the shades and brightness of the day.
It's the environment plays an important part in bichirs colors and patterns, not how you put the lights.
my tank has no light, so it gets dark when is dawn