They get a good amount of daylight and moonlight for that matter because they are near a 8'x2' window. Just no artificial light yet. I haven't noticed any odd behavior from them, and they are very calm when I'm working on their tank. They're also in a very non-traveled part of the house, so they don't see people very often and they still don't freak when I come in the room. Now my bigger silver on the other hand who does have light 24/7 does freak whenever I mess around the tank, and I do that quite often and he still hasn't got used to me.
Yes, they are top water fish, but the areas they inhabit are also fairly shaded by the canopy. I honestly feel that the lights are a main contributor to DE. It explains why in Asia, putting them in ponds causes the DE to go away. Diffused light vs direct intense light.