Understanding UV lighting

[Tyron]

are the reasons people add these lights to their system just for making fluorescence pop, or does it help with coral growth? Or is it used to help make reds,greens, and oranges come to life? I mean i know they make UV sterilizers but im trying to figure out why they're being used in lighting systems, i may want to add it to my build

[lakshwadeep]

The UV light in a sterilizer is not the same as the lighting used for coral fluorescence. Coral fluorescence means red, green, and orange (and other color) fluorescent pigments are visible, but they are not all excited at the same wavelength.

 

A brief explanation of light:

 

Light is an example of "electromagnetic radiation" that act like waves, and these have different wavelengths depending on their energy. As energy increases, the wavelength decreases. These wavelengths are like the wavelengths of liquids.

 

The wavelengths that are part of visible light are in the nanometer (nm) range, roughly from 400-750 nm, which corresponds to the colors of violet (380–450 nm) all the way to red (620–750 nm). Ultraviolet light is the light from 10 nm to 400 nm, and it's called ultraviolet because the energy is higher than violet light. UV light is also separated into different groups, like UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm). UVC lighting is used for sterilization, and both UVB/UVC are normally shielded by earth's atmosphere, so corals aren't used to such high energy light (and lower wavelength UV light). UVA is the majority of UV light that we and coral reefs experience, and lower wavelengths are often dealt with "sunscreen" compounds that protect up to ~360 nm.

 

So, some corals have developed pigments to deal with UVA light. Fluorescence occurs when a pigment absorbs energy (excitation, in this case by light) and emits light at a different energy (and thus different wavelength). Fluorescing light has a lower energy than the absorbed light, which corresponds to a higher wavelength. As you can see, UV light will allow corals to absorb previously invisible light and emit it as visible violet, blue, green, yellow, orange, or red light because those wavelengths are larger than the UV. Violet/blue light are used also for fluorescence, which is why actinic lights (that usually have peaks ~420-460 nm) are so popular. However, not all compounds that give coral colors are fluorescent.

 

Here's one article on fluorescence.

http://www.advancedaquarist.com/2006/9/aaf...iew?searchterm=

[Tyron]

thanx for the reply, this article is very helpful also, but boy is it long. so i take it reefers are just using actincs for their main source of UV?? i mean i dont really read alot about hobbyists buying uv lamps/LEDs unless they go by another name. Does anybody have an LED build with some UV LEDs?

[redfishsc]

thanx for the reply, this article is very helpful also, but boy is it long. so i take it reefers are just using actincs for their main source of UV?? i mean i dont really read alot about hobbyists buying uv lamps/LEDs unless they go by another name. Does anybody have an LED build with some UV LEDs?

 

 

Lakshwadeep said it well, but I'll chime in a nickel or two.

 

Folks aren't generally looking specifically for "UV" lighting when they use actinics. Most actinic lamps put out "violet" light, and a little "ultraviolet" and a little "blue" light. They usually peak at 420nm wavelength.

 

The reason for their use is mostly coloration. This wavelength of light is also somewhat photosynthetically active, meaning it does contribute to their growth.

 

Now, a true "blue" light (450 to 460nm) puts out a very different color and usually puts out a LOT more photosynthetically active light, yet it also produces some very nice coloration. A very good bulb.

 

 

 

There are a lot of folks around here who have use UV LED's----- specifically those around 360nm and up---- in their LED arrays, but nobody is sure if they do anything really helpful. It's more experimental than anything.

 

 

 

NOBODY