Actinic light question???

Question

What are actinic lights and whats its purpose for the fish tank?

Thank you

Answer 1

Actinic lights are a VERY blue spectrum which simulate the deeper water conditions that corals would grow in.  As the water gets deeper, less light penetrates, and the longer wavelenths become weaker, and shorter wavelengths (blue) become more prevalent.  The algaes that they maintain symbiosis with the corals have adapted to these short wavelengths, and are then provided in aquaria with blue lighting, such as actinics or high Kelvin rated bulbs (14,000 and 20,000K are very common).  Compared to 10,000K, actinic is a purer blue, lacking reds, greens, and other areas of the spectrum.  In a freshwater tank, actinics have little purpose, as plants are found in shallower waters where the longer wavelengths (red, green, yellow) are still prevalent.

Answer 2

Actinic lights are intended for saltwater reef aquariums. They emit light in the spectrum needed by photosynthetic corals.