Questions on 10,000k vs 20,000k.

[JmLee]

Hi, im new to the forum and i just had a question. What are the advantages and disadvantages of 10,000k vs 20,000k. Ive heard some people say " sacraficing Growth ?" by using 20k's. The reason why im asking is because im am going to purchase 2X250 watt MH HQIs for my 50gal.

Thanks for any help guys.

 

[Blown 346]

Themain differnce is going to be color, the 10 K's are going to be more of a yellow pigment as the 20 K's will be blue.
But this also depends on the brand of the bulb as each brand has a different coloration.
I myself went inbetwen both and got the 14 K bulbs for my reef and love it.

 

[hahnmeister]

Ill give you the obvious and popular first...

A 20,000K is bluer, so you dont need actinics to suppliment like what is often done with 10,000Ks. The PAR, or photosynthetic active ratiation, which measures the entire visible light spectrum, on a 20,000K is often 1/2 that of a 10,000K, so people who use 20,000Ks often go one size larger (like from a 150wattDE to a 250wattDE) to make up for the diminished output of the bluer bulb. According to some, PAR is the absolute measure of a bulbs output as far as our tank's photosynthetic organisms (corals, algaes, etc) are concerned.

And here's an unpopular view...my view. I think that the idea that 'PAR is PAR' and that is all that matters is not true. Many other photosynthetic organisms use specific wavelengths for certain things. Land plants for instance, use red light for budding, and blue light for growth. Also, when many people's halide bulbs get old they tend to color-shift, and start to put out wavelengths that are considered in the 'extended PAR range', or outside visible light and the light that a regular PAR meter reads. This often causes an algae outbreak because certain algaes like cyano feed on these IR waves. IME, growth with 10,000K's arent much better growing bulbs than 20,000Ks, despite the lower output. It would make sense, as corals under the sea would prolly not have much use for the yellower/red wavelengths that a 10,000K makes...and so we must compare blue range output (420-450nm), and leave out the green and red spectrums all together. When you compare these blue spectrums and the bulb's output between 10,000Ks and 20,000Ks, you will find that their outputs are similar.

Plus, I love the way bluer bulbs make my corals color up. Whats the point of growing corals in the tank if their colors arent as great as they could be?

 

[fadeintoblue]

Thank you Hahn, that's the best answer I've heard for that question.

 

[dannieboiz]

It's strange that you guys are saying that 20k are bluer.

I have coralvue 175w 14k and they're extremely blue compared to the 250 XM 20k as well.. Both SE and the 150w HQI 20k.

All of the 20k that i've seen tend to be more white with a very very light tint of purple.... Definitely not blue.

Go 10k + actinic sup. Brighter tank and more natural IMHO.

W/o the act. sup, you'll hate it for sure though. You'll definitely see the yellow. I have one t5 SO actnic only and I don't even notice the yellow anymore..

 

[JmLee]

for every one that took the time to reply, THANKS! and hahn good stuff.

 

[Mattw2190]

What about 14 or 15k's are they really the happy medium?

 

[werew]

Dannie,
I have a 175watt MH Coralvue 10k and it has a nice blue tint to it, looks great. I'm going to add 2 T5 HO actnic plus's to it for low light & dawn/dusk supplementation.

I'm really liking my Coralvue so far.

JMLee,
2 250watt bulbs for a 50 gallon? That's going to be VERY bright, have you considered two 150/175 electronic HQI ballast "based" setup? That might be a better choice for a tank of that depth?

 

[dannieboiz]

<a href=showthread.php?s=&postid=6539887#post6539887 target=_blank>Originally posted</a> by werew
Dannie,
I have a 175watt MH Coralvue 10k and it has a nice blue tint to it, looks great. I'm going to add 2 T5 HO actnic plus's to it for low light & dawn/dusk supplementation.

I'm really liking my Coralvue so far.

I've never seen 10k coralvue up front, but the 14k is def. blue. I have 10k hamilton on hamilton ballast and they are slight yellow.

 

[hahnmeister]

dannieboiz,
Well, all the colors are natural...it just depends what depth you are comparing the bulb to. As for the blue, it is interesting that you bring that up. I didnt want to get too technical here, but since you brought it up...

Most 10,000Ks have a rather flat curve from the 400-700nm range...lots of little spikes, but nothing crazy. But heres the funny part, a 10,000K usually has just as much purple (420nm spike) as a 20,000K. What makes a 20,000K is that from 480nm to 700nm, the output is much lower, and there is a noticable spike in the 450nm (blue) spectrum. So a 10,000K and 20,000K have the same amount of purple really, its just that the rest of the spectrum covers it up with a 10,000K bulb. This is even true of a 6500K Iwasaki. If you compare spectral graphs, the 6500K has just as much blue and purple as a 10,000K, if not more.....its just the extra green, yellow, and red spectrums that cover it. now, if you look at most of the newer 14,000Ks, even though they have a higher K rating than a 10,000K, its because of their huge blue 450nm spike (and lower warmer K levels). Really, the only difference between a 14,000K and a 20,000K (I have looked at many, but in particular, look at the spectral graph of a pheonix 14,000K compared to a radium 20,000K) seems to be the lack of the purple 420nm spike. A 10,000K has more purple than that (many 10,000Ks have more purple than 20,000Ks in fact...you just dont see it).

I like the look and growth I get with bluer bulbs. The corals just seem to grow just as fast and with more color. To get the same amount of blue with halides, you need at least 1 watt actinic/blue per every 2 watts of 10,000K halide, if not 2 for every 3.

 

[supertech3]

Dannieboiz,
the color difference from 10k up to 20k should be bluer because it represents the difference in depth of water. The deeper you go into the ocean the bluer it gets that is more colors are filtered out of the light spectrum and thus creates blluer light. I know that not all bulbs have a true representation of this that is why we look at graphs to see how well the bulb manufacture has done to replicate this.

 

[dannieboiz]

Ok but most people don't have such eye to see all the different color sprectrums with their naked eyes.

If we're comparing looks for looks with naked eyes, i like 10k with subs. To my eyes they look brightest. I also noticed more ripples on the rocks with 10k compared to my 14k.

 

[werew]

I havent had my Coralvue 10k's for long, so the blue tint might not stay for long... although i wish it would.

I have two 39watt T5HO blue+'s for actnic supplementation but at this moment I dont even need them really.

 

[JmLee]

Werew i ordered 2x250watt 15000k metal halide HQI aquamedic pendants..... thats about 10watts per gallon, with that much lighting on a 50gal i should be able to stack anything anywhere hehe.

 

[DKreefkeepers]

I got the 14k hamilton and I like those, I get good PAR with the PFO balast.