460nm vs. 67000K???

[Reef Bullet]

My fixture holds 2 150watt MH bulbs and 2 96watt PC's

I need to replace all the bulbs because they are old and I am trying to figure out what to order.

I have pretty well decided on 2 14000K Phoenix MH's but I don't know what to order for the PC's so I need everyone's advice! I would like to get blue bulbs for the PC's but want to have enough wattage for my 70gal tank to allow for coral growth, but I also want to have the correct spectrum. I have a mixture of SPS, LPS, and Softies. My tank is approx 20" deep and the lights are approx 6" above the surface.

I have spent a ton of time online reading about lighting, but frankly a lot of it is over my head b/c I don't think I have the basic understanding that I need to understand the more complicated stuff and how to choose the best bulbs for my tank and inhabitants. I have read that actinics do little for coral growth... Is this statement talking about only the 420nm's or all bluish bulbs?

If I understand right, 420nm is more purple than blue and definitely not good for growth, but I'm not sure about the 460nm or the 67000K. Is this right? What is the difference between 460nm & 67000K?

Thank you in advance for your advice!!!

 

[Flame_Angle]

Don't know much about 67000K? But the 14K is good for them tp grow. You can do Actinic blue for the PC.

 

[coachfraley]

6700k is a spectrum for growing plants, get the 460

 

[Reef Bullet]

Thanks. So 460 will help with growth?

 

[El Dude]

Get 14k halides and 460nm PCs. 460 is a baby blue to the eyes...it will look crisp. But if you want to have that deep blue feel go with 20k halides...I'd stick with 14k though..

 

[Reef Bullet]

Thanks, Al. The crisp light blue is what I'm going for... But just to clarify, will the 460's help with growth or just with color?
Thanks for helping my newbie-ness!

 

[rayray]

The physics:
"nm" is nanometers, or 1x 10exp -9 meters. this distance is a complete wavelength, which is a physical property of any wave (such as light, aka "electromagnetic radiation"). wavelenths of light in the "visible" length have an associated absolute color.

kelvin is absolute temperature, and "kelvin scale" in lighting color is the hue or appearance of visible light as if it were from a "black body" at that temperature. it has a subjective or psychological component of appearing more "warm" (yellow) or "cold" (blue)

The biology:

photosynthetic coral have zoxanthellae algea that captures light of different wavelength. 420 nanometers is very useful to coral.

That is different from the appearance of color to the eye reefers appreciate. americans like their tanks more blue, or in the 14,000-20,000 kelvin look. 6700 kelvin appears more yellow. it will grow coral, but not as well as 10k Kelvin appearance, which has more blue wavelenth and colder appearance.

Whats the best? not even PhD engineers (like Sanjay Joshi) or coral biologist PhDs know for sure. But hopefully this lets you get some foundation so you can make your own decisions.

HTH

Dr. Joshi's lighting guide for MH & LEDs: http://www.manhattanreefs.com/lighting

light kelvin rating and coral growth: http://www.advancedaquarist.com/2008/3/aafeature1

T5 light output comparisons: http://www.advancedaquarist.com/2009/3/review/

the "best" light: http://www.advancedaquarist.com/2008/12/aafeature1/view?searchterm=metal halide

latest in LEDs
www.advancedaquarist.com/2012/3/aafeature
http://www.advancedaquarist.com/2010/5/aafeature2
http://www.advancedaquarist.com/2012/1/aafeature

 

[El Dude]

Thanks, Al. The crisp light blue is what I'm going for... But just to clarify, will the 460's help with growth or just with color?
Thanks for helping my newbie-ness!

Both...but don't fear. Those halides are powerhouses. You're going to meet the lighting requirements of 99% of what's out there.:dirol:

 

[Reef Bullet]

Thanks rayray!
However, part of me understands better now, and part of me is more confused. I used to have a PC only fixture (briefly and before I got into corals) and had one 10000K & one 67000K. I have always thought that the blue one was the 67 and the whiter one was the 10. I'm not sure why I have always thought this, or where it started, but apparently I got confused somewhere along the way! I am still confused, though, b/c from my reading online and looking at the charts you posted as well, it looks to me that the higher the number, the bluer the color. So why is the higher 67000K yellower than the 10000K? Where am I getting lost???
Also, you said that the 420 will provide a good photosynthesis for corals? So if you were me, and your fixture would only accomodate 2 150w halides and the 2 96w PC's, AND you wanted a crisp blue look (not too deep/dark blue so as to keep the tank bright, but still have the coral colors pop), what bulbs would you buy???
Thank you so much!!!
Lindsey

 

[Reef Bullet]

Both...but don't fear. Those halides are powerhouses. You're going to meet the lighting requirements of 99% of what's out there.:dirol:

Thanks Al,
I am a little scared, lol... I'm about to break the bank buying bulbs and I don't want the few corals I've gotten to die! So I want to make sure I don't buy the wrong bulbs! I know many people have experimented with different specrums and types, but I don't have the money to do that so I am just hoping to be able to use the experience of the old pros and get the right ones the first time!


Oh, and 300watts of halides are enough for 70 gal? I thought I needed at least 5 times per gal of wattage if I want to have SPS. (350watts) Plus, the halides only shine on either side of the tank and the middle doesn't get much of that at all...

 

[rayray]

So why is the higher 67000K yellower than the 10000K? Where am I getting lost???

if you were me, and your fixture would only accomodate 2 150w halides and the 2 96w PC's, AND you wanted a crisp blue look (not too deep/dark blue so as to keep the tank bright, but still have the coral colors pop), what bulbs would you buy???

Physics nerds have extrapolated that the theoretical "black body" burning at 6700 degrees kelvin (not 67,000) would look yellow to our eyes, if it burned at 10,000 degrees kelvin it would appear white, and 20,000 degrees kelvin blue. its not a property given by nature, just a convention developed by people, just a given we have to accept.

most people say "actinic" PC bulbs make certain coral pigments fluoresce or "pop." there is controversy if it is really good for the coral, but look at the photosynthesis picture and you'll see chlorophyll A has a major absorbance at ~420nm, so I think it is helpful. also, when you go to coral trade shows everyone has their coral for sale under very blue actinic light because it makes them look more attractive- $$$.

now for the main lighting, metal halide, crisp white light can be acheived with lamps in the 10-20kK range. a good bet would be 14 kiloKelvins. it gets more complicated because every bulb looks different when powered by different ballasts. also, there is a lot of personal preference involved. I recommend using this link and inputing your ballast with the all the bulbs you are considering.

Dr. Joshi's lighting guide for MH & LEDs: http://www.manhattanreefs.com/lighting

actinic pc + MH 10-20 will definitely grow your coral, so dont stress out, have fun with your choice!

 

[Reef Bullet]

Physics nerds have extrapolated that the theoretical "black body" burning at 6700 degrees kelvin (not 67,000)

Well THERE is where my confusion is coming from!!! :a42: I thought it was 67000 not 6700!!! Thank you so much for clarifying that, rayray!

Now... if I can ask one more question... I have read that the 420nm is more purple and will make the corals pop more than the 460nm that is more blue, but that the purple is not as bright. I feel like I need the extra bright because the MH's being on either end with a fairly long empty space in the middle leave things kind of dark and my tank is a good 20" deep plus the 6 or more inches above the tank where the lights are. Right now I have one 20000K MH & one 10000K MH with 2 "Blue" PC's. (Blue is all the bulbs say and these are the bulbs that were already in it when I bought them from someone with a tank purchase off craigslist.) I feel like is is a little dark on the 20K side... It doesn't bother me much but I wouldn't want it any darker. The 10K side is bright, but it is way too yellow.

Is there anyone who has used both the 420 and the 460 bulbs that can give me their opinion of the two? Does the 420 give your tank a real purple look and is it a lot darker than the 460 blue? If I want a crisp blue color but want bright light, AND to have the corals pop, am I asking the impossible?
THANK YOU!!!