i know what actinic is, but what is it?


New member
I know actinic is usually referred to as blue lighting. But what is it really? Are ati blue plus considered actinic? Are blue leds like blue reefbrites considered actinic?



Premium Member
No. Actinic is 420nm. I am pretty sure blue+ are 460nm. Close but actinic is more purple. Reefbrights are closer to blue+


Premium Member
Just to throw in useless information actinic light used to mean light that would expose photographic (B&W) film - ie the green or blue parts of the spectrum. A non-actinic light was a safe light - ie a red light in a darkroom.
But now as tkeracer619 says, it customarily refers to light that peaks at 420 nm - violet. Blue is defined as peaking at 470 nm.

The ATI Blue+ is advertised as having a combination of 460 and 420. The ATI True Actinic is spec'd as peaking at 421 nm.

Here is a link to the info from ATI showing the spectra of its T5s. http://www.atinorthamerica.com/cmsAdmin/uploads/ATI_Datasheet_T5bulbs.pdf


New member
A look at wikiepedia and a quick Google search reveals answers.

Actinism refers to the radiation that produces photochemical effects.

Actinic light is light that has the characteristics of actinism

Wikipedia further defines actinic light as light having photosynthetic effects

In reef aquaria were normally referring to light at wavelengths from 410nm all the way up to 480nm.