"There are aluminum light bulbs that can mimic the light spectrum and wavelength of the sun and the moon. Metal halide lighting is the popular light source used in reef aquariums. The high output lights of this kind of light source can imitate the shimmering effect of sunlight. The bulbs of this kind of light source for marine aquariums can come in various spectrums.
There are light sources for aquarium that can mimic the light of the moon. Called aquarium moonlight, this kind of light source can be decoratively placed in an aquarium. Although not as bright and powerful as metal halide lighting, aquarium moonlight can provide advantages to aquatic creatures.
Aquarium moonlight is a light source that is composed of specialized LEDs. The LEDs can produce wavelengths similar to that of the moon. It could be used in conjunction with metal halide bulbs. While metal halide bulbs can produce day-time environment for fish, corals and invertebrates, aquarium moonlight can be used as nighttime light source for the aquarium creatures."
I know you said that you were into freshwater but I'm not sure how much that would very from freshwater and saltwater.
--Information found at
- Aquarium Moon Light