First of all, are you talking about the actinic bulbs for reef aquariums or are you talking about the lunar lights that some lighting systems have built into them?
- If you are talking about the actinic bulbs, NO, do not use them. They don't exactly hurt the plants or fish, but freshwater plants won't be getting the needed lighting requirements. In general, just stay away from them.
- If you are talking about the lunar lights that are built into some lighting systems (which I think you are), they are fine to the best of my knowledge. I actually prefer having them in my freshwater tanks. I think it helps simulate a natural lighting system and it produces a little light so you can view them at night without having to put the lights on and mess with the fish. I couldn't say for certain whether it messes with the plants "down time" at all, but I really don't think the light is of a significant enough intensity to disturb them.