Actinic Lighting

Actinic Lighting

Author: Think Fish Last updated: 20 February 2014 13:39

Actinic is a term used to describe lighting which produces high levels of light in the blue wavelengths.

This type of light is important in aquarium use as the blue wavelengths of light penetrate water far deeper than other visible wavelengths. Blue light is at the lower end of the light spectrum and is more 'energetic', allowing it to pass through objects further before it is absorbed. Sunlight peaks in the blue areas, because other wavelengths are absorbed as they pass through the atmosphere; the same happens in water (which is why the ocean appears blue) In typical pictures of tropical islands, the surrounding water is a light blue; this is because sunlight travelling through the water is absorbed at different colours or wavelengths, and blue light, being the most energetic, is the least absorbed and hence, most reflected.

Photosynthetic organisms such as plants and algae's are adapted to utilize the blue wavelengths of light, because they are more readily available underwater.

Actinic lighting is designed primarily for marine aquariums, where some corals depend on the algae cells living within them to provide a source of food. The more actinic, or blue light, is produced - the more light is available to the algae.

Actinic light can also be used in freshwater aquariums and is useful for plants, but may produce a slightly unnatural effect. When used in marine aquariums however, actinic light used in conjunction with a bright white light, has quite a pleasing appearance.

Many high-powered lighting systems designed for marine reef aquariums incorporate actinic lights to 'balance' the light output and ensure that corals lower down receive enough light.

Actinic light is different to ultraviolet light, which is even more energetic but outside of the visible spectrum and used for a different purpose.

The dazzling fluorescent colors of corals under actinic lights

The kind of light that we see things in changes how we see those things. This reef tank is shot under actinic light, which will not only facilitate photosynthesis or stimulate light sensitive species, but also changes how the corals look. From

The light spectrum, or Kelvin rating, of aquarium lighting will also alter the appearance of corals. For example, bulbs that emit light heavy in the actinic blue range bring out dazzling fluorescent colors not visible under full spectrum daylight bulbs. While different hobbyists prefer different combinations of light spectrums, a typical lighting system for a reef aquarium consists of 50% white light with a high Kelvin rating and 50% blue, actinic light.

It’s also a lovely video of reef life to boot. Watch more coral videos on this site.

Top 24 Best Actinic Aquarium Lights of 2022 (Reviews)

Choosing the best actinic aquarium light can be difficult as there are so many considerations, such as Helios, Aqueon, Coralife, Fluval, 21 LED. Luckily, we've researched for you and also put together a list of our top 24 Best Actinic Aquarium Lights for you to consider.

We have spent more than 79 hours testing a lot of actinic aquarium lights with prices ranging from $11 all the way up to $176. One of our favorite is Helios Aquarium Light. The other recommendations on this list are also worth considering, and we also created a handy buying guide to help you make your choice!