what do the blue lights do?

[repelking]

Could someone explain to me what the blue lights do in aquarium lighting setups? I know they take away the yellowish appearance of regular flourescent light, but do they do anything for the health of the occupants? And is it something only used for reef tanks?

...I need enLIGHTened on this subject

(I know, that was bad, but I would like to know.)

 

[reeffreak]

If you are asking about true actinics(purple bulbs) then no they are not needed.It is use more for looks and make corals flouresce.

Corals do use light in the blue wavelength.Generally,there is enough of the blue in many daylight bulbs but people still prefer blue bulbs to balance the wash-out look of only just daylight bulbs.

 

[Brian_G]

in the ocean the blue tint comes from the fact that blue light can penetrate more water and go deeper.
Yellow and reds are reflected and refracted and become undetectable shallower.

But in our case, its mostly for looks

 

[repelking]

cool, thx. always wondered, but never asked.

 

[Charliegrs]

So are actinics the kind of lights you want for corals? I always heard that blue light is the type of light that corals photosynethsize and actinics are blue. Im kind of confused about it.

 

[reeffreak]

Only purple(420nm) bulbs are considered true actinic bulbs.Some blue bulbs are often called actinic,yes some light in the blue spectrum is needed so in a sense actinic blue bulbs are needed.

 

[BL1]

So are actinics the kind of lights you want for corals? I always heard that blue light is the type of light that corals photosynethsize and actinics are blue. Im kind of confused about it.

Not necessarily, you don't need actinics over your tank to have corals, I along with plenty of other people don't have them and are quite successful in keeping corals. Corals don't necessarily photosynthesize under blue light, what you really want to look for are lights/bulbs with a higher PAR rating (photosynthetically active radiation). The higher the PAR value, the more usable light your corals are getting. Actinics are mainly used for supplementation to whiter or yellower bulbs to help bring out the colors in your tank.
I hope this helped. Here's also an article that was written about reef lighting and some detail about all the options available Lighting the Reef Tank: A Primer for Beginners by Doug Wojtczak - Reefkeeping.com