10k vs. 20k

[Scott Clendenin]

I've been comtemplating the switch from 10k to 20k MH. I prefer the softer look of the 20's, but one LFS says calcification of my stonies will be stunted, another LFS states the 20's will accel their growth. These statements are generalizations on their behalf. I've also heard dramatic morphs may take place from such a change in light. Who's made the change, and what should I expect? Would you recommend changing?
Scott

 

[JeremyR]

I personally don't like the 20k lamps, generally much less intensity watt for watt. I've seen alot of people go from 20k to 10k and have better results.

 

[Anonymous]

JeremyR wrote:
I personally don't like the 20k lamps, generally much less intensity watt for watt. I've seen alot of people go from 20k to 10k and have better results .
i agree- the 20k's actually look darker-like the ocean at a greater depth, much more visibly blue.though if you've got a fairly large/long tank(what size is it?),you may want to try one bulb at one end.replacing only one of the bulbs first, and waiting, will let you know(prob'ly within a month) if any harm will be done, if the 20k is what you prefer.(the corals will prob'ly just have to adapt a bit, imho)

 

[Scott Clendenin]

Jeremy,
The loss of intensity you speak of, is this in appearance or is there some reference I can look up? I was under the impression that the 20k have an equal intensity, it was just on the blue end of the spectrum.


As for my tank size, its pretty small, 46gal. I currently use 2 175w MH, but would switch ballast to one 400w if I was to make the switch. I have other tanks that could use the supplementation of the current 175s.
I also heard nuisance algae is less prominent in 20k light.
Either of you guys have an opinion on the calcification rate under these lights?
Scott

 

[JeremyR]

Sanjay has tested several of the 20k type lamps, and they were generally 1/3 the par of a daylight type halide. The only 20ks worth messing with are the radiums, but I still don't think they hold up next to the 10k's or 6500 iwasakis.. every few years there is a rash of people that get on the 20k bandwagon, then it goes away for awhile when they find out it's not that great of a bulb (IME).

 

[RicardoMiozzo]

20000K is too blue, and lacks light in the white / yellow spectrum.
10000K is the most sunlight like of the bulbs I know.

 

[Bodine]

Well I guess i got on that "bandwagon" back in `97 and have never gone back to 10K.....I agree that Radiums are the only way to go...and only in 400 watts........
Signed.....
Dedicated 400 watt radium user...

PS.......Beg to differ......Radiums are not "too blue"

 

[moeb]

i just switched from 400w 10000k to 20000k radium with an HQI ballast i think its a much better light than the 10k but thats just my opinion

 

[xKEIGOx]

hemm... i'm not sure but I think 20,000K and 10000K won't have much deferent with the coral. just for your eyes. I personally like it in blue and not so intense... more like the ocea. :wink:

 

[Gary Majchrzak]

Did you guys read the transcript of Steve Tyree's recent discussion regarding these MH lamps?
I've found combining 10k with 20k gives excellent results.

 

[john f]

"Sanjay has tested several of the 20k type lamps, and they were generally 1/3 the par of a daylight type halide. The only 20ks worth messing with are the radiums, but I still don't think they hold up next to the 10k's or 6500 iwasakis.. every few years there is a rash of people that get on the 20k bandwagon, then it goes away for awhile when they find out it's not that great of a bulb (IME)."



You guys really need to learn to think for yourselves. Have any of you guys dismissing the 20K Radiums ever actually used them?

Sanjays testing has always been seriously flawed. While I appreciate his efforts, he has always rewarded light output in the 500-600nm range with the same importance as light in the 400-500nm range. This is the problem with using PAR as the yardstick.

Corals do not use light much at all in the green/yellow/orange parts of the spectrum (500-600nm) and the Iwasaki puts out 60% of its "PAR" in this range.
Look at a graph of the absorption spectrum for corals, or chlorophyll A or the chlorophyll A/peridinin complex and you will see that light from 400-500nm is the most important for corals, with a peak absorption at 450-460nm. The Radium 20K bulbs put out twice as much light at 450-460nm as an Iwasaki, and even more when comparing to 10000K AB or Ushio bulbs.


I agree with Gary that the combo of 10000k and 20000K bulbs looks to have the best light output for corals, as well as pleasing to the eye.

If I were Scott I would add a 20000K to the 10000K and lose the actinics. But this does not really serve his purpose of saving a few bucks.
If he only wants to run one halide with no actinics then I think the 20000K Radium at 400 watts would be the way to go, on the correct ballast.



John

 

[Timbo1]

Corals do not use light much at all in the green/yellow/orange parts of the spectrum (500-600nm) and the Iwasaki puts out 60% of its "PAR" in this range.
Look at a graph of the absorption spectrum for corals, or chlorophyll A or the chlorophyll A/peridinin complex and you will see that light from 400-500nm is the most important for corals, with a peak absorption at 450-460nm. The Radium 20K bulbs put out twice as much light at 450-460nm as an Iwasaki, and even more when comparing to 10000K AB or Ushio bulbs.

Would you care to list a source where I can find one of these graphs?

 

[john f]

Sure:


http://www.chm.bris.ac.uk/motm/chloroph ... hyll_h.htm
http://www.reefs.org/library/talklog/s_ ... /acpPC.jpg
http://www.reefs.org/library/talklog/s_ ... 02/pas.jpg


John

 

[esmithiii]

Here are some links:

http://www.animalnetwork.com/fish2/aqfm ... efault.asp

http://www.personal.psu.edu/faculty/s/b ... rison.html

 

[esmithiii]

10000K is the most sunlight like of the bulbs I know.

Also, technically speaking, sunlight is in the 5000-6000 Kelvin color temp range.

 

[john f]

"The Radium 20K bulbs put out twice as much light at 450-460nm as an Iwasaki, "

I would like to ammend the above statement.
The Radium 20K bulbs put out 6 times as much light at 450-460nm as an Iwasaki.

Sorry, I was typing fast and not reading the graphs correctly.


John

 

[eddie]

john f
thanks for the links
as you already know i love the 20k radium mainly for the look
but as you mentioned
i plan to mix them with some 10k ushios (on 400 watt s-51 hps ballasts)
over sps vats
iwasakis suck imo (they look horrible and you can run 3 400 watt 20k radiums and be better off than 2 400watt saki's and atleast 360 watts vho actinic)
not to mention how hard it is to mount the vhos and halides together compared to just hanging a few pendants

 

[esmithiii]

over sps vats
iwasakis suck imo (they look horrible and you can run 3 400 watt 20k radiums and be better off than 2 400watt saki's and atleast 360 watts vho actinic)

A couple of things to consider... the life of the bulbs and cost are big considerations, especially if you are putting them over SPS vats! the look of the bulb is less of a consideration if it is over a grow out tank and not a display aquarium.

I have iwasakis and I use PC actinic supplementation. I like the look, and the growth is incredible. I think in a display aquarium, the best is to mix bulbs, possibly 6500K and 10,000K or 6500K and 20,000K bulbs. I don't know of anyone who has the iwasakis that complains about growth rates, which is what you are looking for in grow out tanks, IMO.

Iwasaki bulbs should be replaced, IMO every 12-18 months (compared to 9-12 for radiums) and costs half what a 10K bulb does, (a little more than half of the cost of a 20K bulb also.)

Most of my corals' coloration has improved under the iwasakis also. I do wish the tank looked bluer, and may mix a 10K in with 2 6500K bulbs.

Again, just my opinions.

Ernie

 

[eddie]

i havent dismissed them for use over vats (yet)
but the grow out vats will be in a greenhouse
& the 20k-10k mix vats will be inside to color them up for tading -selling
some sps corals color nice under saki's purple & blues
but the greens yellow etc...and such dont in my experiance
and most softies & lps under saki's cant compare to ones under 20k (imo)
but i may use a few saki's for the few that color nice under them

 

[JeremyR]

Yeah, that's what I always find interesting about these lighting arguements. The 20kers make it sound like iwasakis are horrible lamps for corals, but the growth you get with them is outstanding. Hey, people are allowed to have differences of opinion. The old saying goes, there is more than one way to skin a cat. Whatever works for ya.