[sgarron]

10k, 13k, or 20k. Which one?

[mtfabel]

Depends on what your end goal is. The higher the number the more blue the light will be. 10k is the best for growth of corals but 20k makes the corals look better in your tank.

[NATIVEVAMAN]

There is a substantial amount of evidence to indicate that the best coral growth occurs under lights around 6.5k.Thoughts on Reef Aquarium Lighting… Keep Your Eye on the Prize! by Anthony Calfo- Reefkeeping.com

[Six-line Wrasse]

6,500°K is the best for coral growth, while it also may be the best for rare colored coral coloration. 20,000°K is more like an actinic bulb and provides better coloration through color fluorescence, similar to a black light.

[Krazy]

I just love the look of dual actintics and 20k bulbs !!!

Talk about having the color pop out !

[mtfabel]

OK I agree that 6500K bulbs are the best for growth but I personally cant stand the color of anything less than 10K. I guess I should have stated that in my first post.

[kh6sat]

I was wondering what a 6.5 would look like. I don't really care for the color of a 10k running by itself. I usually run my 10k's with the actenics on as well. 10k is too yellow to me, by itself.

[Fishhead Junkie]

i just noticed that today with my bio-cube...i was adding some tigger pods into it...so i hit one of the switches and i turned off the atinic lights by mistake and the tank color looked like crap. its amazing how just 1 bulb can change the whole color scheme of your tank. i sort of wish the bio-cube came with more moon lights. they only seem to hit a couple of my corals and i really dont feel like moving them around to accomodate what light i currently have. oh well. its almost 12:30am, time to get out of work and go home to some food and a beer!!!! booya

steve

[Six-line Wrasse]

6,500°K bulbs are typically very yellow. You can even this out with actinic bulbs or higher Kelvin bulbs. When you purchase bulbs, make sure they're actinic and only actinic. Often times you'll buy bulbs that are called Blue bulbs and these are simply bulbs in a blue glass cylinder or coated with blue light-emitting phosphors which do not have the same PAR advantage as actinics due.

[kh6sat]

Is there any significant difference as far as reef life is concerned between Actinic Blue (460nm) vs Actinic Blue (420nm)? I prefer 460nm because its more blue than the 420nm. 420nm has a little bit of a purple tint. The LFS said that the 420nm is the most used actinic.

[Six-line Wrasse]

Both are good.

460nm and 420nm refers to the distances of each individual light wave in nanometers. So, the shorter the light way the closer to the unseen ultra violet spectrum and the more purple the light wave will appear. The higher the nanometer value promotes a more blue to red spectrum.

However, both are close enough in the light spectrum to do a well enough job in your tank, I believe it to be more personal preference then scientific fact.