Making 10k appear blue

[JoeESSA]

I have been looking for a solution to get a bluer appearance in my tank without sacrificing PAR. I have 2x 250W 10k XM halides and 2x96W PC actinics. Up to recently I considered either changing to 20k bulbs or adding more actinic. I did not like the first idea because the PAR gets cut in half so, I experimented with adding more actinic PC's. Since I have a commercial all-in-one fixture it was difficult (lack of space) to modify the fixture to fit more PC actinics into it so I simply experimented by mounting the bulbs over the tank. To cut a long story short adding more actinic did not change the appearance significantly. The overall light became perhaps a little more purple-white, but that's it...

Revisiting the spectral analysis on Sanjay's website one thing occurred to me. The XM 10k's and many other 10k bulbs have a big spike at 420nm (violet) whereas 20k bulbs have a spike at 460nm (blue). The XM 10k's do not have much output at 460nm. So, based on this instead of adding more 420nm actinic I just swapped out the existing 420 actinics with 460nm actinics. Voila! Quite a strong overall blue appearance approaching 20k bulbs, but with the intensity of 10k bulbs.

Just thought I'd share those findings, albeit perhaps obvious to others...

[Ti]

Great to hear it worked!

[Gundo5000]

Any before and after pics? :D

[iamquockie]

arent the 420nm pc actinics very very dim? pretty purple too.
good decision on the switch. u could always do a 12k bulb for a little more blue.

[JoeESSA]

I'll try to post some pics when I get home. The camera lies a little so it may be a bit miseleading. I've never been able to find a good setting with my camera that gives a 100% accurate representation. In general my shots turn our a little warmer, more yellow than than reality.

One thing is clear is that there is now a distinct blue hint to the water (previously white), reds are redder and greens are greener with the 460nm actinic. Before with 420nm the red colors were a more rusty/brown in appearance. Purple coralline algae is purple-blue and darker, instead of the deep vivid purple with 420nm actinic. Also the Xenia now has a greyish-blue hue instead of cream-pinkish-brown which may be a little less attractive. It's all down to trade-off's and preferences...

[JoeESSA]

Iamquockie, that my point. Going to 12k, 14k, 15k, 20k or even some of the blue "10k" bulbs (e.g. Reeflux) would mean losing PAR and full spectrum lighting. The XM 10k's are almost unbeatable for PAR using regular magnetic ballasts.

[Ti]

XM 10k is great on par

[JoeESSA]

Here's some before and after photos. They're not 100%, but fairly close...

2x250W XM10K's with 2x96W PC 420nm Actinics. In reality looks more white

http://reefcentral.com/gallery/showphoto.php?photo=186612&papass=&sort=1&thecat=500

Now, same metal halides with 2x96W PC 460nm bulbs. Closest I could get with the camera. Still gives false impression in some areas, but reasonably close

http://reefcentral.com/gallery/showphoto.php?photo=186613&papass=&sort=1&thecat=500