Plants natch would proliferate in a 100% dark nite, but mother nature doesn't do that so plants adapt. moonlight (being so weak) doesn'treally affect plants, but a bright light closer up shocks the plants into thinking it's daytime and starts to try to go into daytime grow cycle. so a little weak light (like a light leak from a shelf next door) won't hurt them, just keep it dim or use a 'green' light, apparently this color does nothing to plants, so if need be you could 'check' on your dark plants with a green tinted flashlite.