20,000K MH vs. Supplemental Blue Light

[shawnhardy]

What are the trade-offs of using 20,000K metal halide bulbs vs. 10,000K bulbs and supplementing the whiter light with actinic PCs, VHOs or T5s. Is it worth the extra cost of having the supplemental lights? Or does a 20,000K get the job done?

 

[golfish]

It just depends on what you want and like...I have done all of they above. The only reasonI run actinics is for the late night glow in the house. My wife and I always liked that look.

 

[shawnhardy]

So besides looks, most people do it just so they have more watts?

 

[thegrog]

No, most people do it for looks. The extra watts from actinics really do not buy you much in the way of helping out corals as the spectrum of actinic light is not enough to make much of a difference.

 

[hurt]

TheGrog, I couldn't disagree more. To say that actinic's are just for look and have no impact on your corals is garbage. True actinic's peak around 420 nm, a very useful spectrum to corals. For the first two hours each day I run only my VHO actinic's, and believe me, my corals and anenomes love'em. Blue is the most penetrating spectrum into H2O. That is it is the last to be filtered out. They help alot IMO.
http://www.netpets.com/fish/referenc...ielbook12.html

 

[shawnhardy]

I agree that corals need blue spectrum light. I am trying to figure out why we see so many metal halide 10,000k bulbs in the same fixture with some supplemental actinic light.
Someone please explain the difference between 2x250W 20,000K metal halide bulbs and 2x150W 10,000K metal halide bulbs supplemented with 2x96W PC actinics. The wattage is almost the same.
What are the reasons to go with either setup or are the basically the same thing?

 

[ty_05_f]

I feel that intensity outweighs other factors. So in your case shawnhardy, without a doubt, I would get the 2X250 watt MH.

 

[22caddy]

Green, yellow, and red corals need the light spectrum of 6.5k to 10k to do best. Purple and blue corals need the acitinic or 20k spectrum to do better. Most people from what I have read feel they get better growth with 10k.

 

[reefnut]

Someone please explain the difference between 2x250W 20,000K metal halide bulbs and 2x150W 10,000K metal halide bulbs supplemented with 2x96W PC actinics. The wattage is almost the same.
Well first off, wattage is doesn't mean anything when comparing MHs to PCs. Watt or Watt, MHs will produce more PAR (usable Light) than PCs.
To say that actinic's are just for look and have no impact on your corals is garbage.
This is what I read... "The extra watts from actinics really do not buy you much in the way of helping out corals as the spectrum of actinic light is not enough to make much of a difference." and I agree with that 100%.
Blue is the most penetrating spectrum into H2O.
This is true BUT it's not the only spectrum that can be utilized during photosynthesis.
The 6500k MH is known to produce the greatest growth in corals... not because they are heavy in the blue spectrum (because they are not) but because they produce the most PAR (usable light).
The 20k MH will produce the slowest growth... although they are heavy in the blue spectrum.
What are the trade-offs of using 20,000K metal halide bulbs vs. 10,000K bulbs
The trade off is color for growth. If you want good growth go with the 10k bulbs... and add actinics if you like the bluer look.

 

[nm reef]

In part your question seems to be why use 10K MH's along with actinic suppliments instead of just using 20K MH's without actinics.....
In reference to that part of your question....
I like to simulate dawn/dusk on my reef...the actinic VHO's come on 1.5 hrs before the 2x400 watt 10K MH's.....then remain on for 1.5 hrs after the MH's shut down.....during the 8 hrs all the lights are on (2x400 MH's & 2x110 VHO's) the effect is like high noon....crisp white. The effect prior to the MH's and after the MH's is for my personal viewing pleasure primarily....and in my opinion that effect can not be touched using only 20K MH's....hope that helps answer part of your questions.

 

[sammiefish]

I just wanted to comment on one of my experiences. My observation was not made during a controlled experiment but... I think its possible to provide too much light. A friend and I obtained Montipora caporcornis frags from the same parent. I initially used an aqualite then 20000K MH + VHO actnic ... the sibling frag was under 10000K MH right from the get go. My frag is really orange/red... the sibling is light washed out pinkish.. mine increased size doubling in size about every month... the sibling grew about 1/8 and inch in 6 months..but the plates were thicker. (acroporas in the tank with the sibling seemed healthy too and did show some, but not alot, of growth) I have no acropora as of yet.
Yes, the water quality could be different but I think the biggest difference is the lights.... (again not a controlled experiment)....
when I changed from the aqualite to the 20000K MH's the color seemed to get a bit more red... and the plates became thicker...
so... my guess relative to Montipora caporcornis... more light intensity gives thicker plates... bluer spectrum produces MUCH mor desireable color.... (not just with the lights on, but real color)
BTW, doesnt Dr. Macs use 20000K XM's?
just my observations

 

[reefnut]

Water quality, water movement, alkalinity levels, stableness, etc has more of an effect on actual color than lighting IMO. Appearance though, is IMO better under 20k bulbs.
My experience is just the opposite. I was running 10k XMs with VHO actinics and switched to 20k XMs and only using the VHO actinics for dusk/dawn. I have noticed a MAJOR decrease in growth. My acros and other sps corals have slowed considerably... and the ONLY difference is the lighting.
IMO, if you're happy with your lighting and your corals are healthy... that's all that matters.

 

[sammiefish]

yes, in many ways your observations were "more controlled" but time and what is going on during that time are variables so lights are not the "ONLY" thing that was different...
Of course your observations make perfect sense to me.... and like I said, my observations were not made during a controlled experiment.
Also, let me restate... the change from the aqualite to the 20000K MH produced thicker plates..... and the sibling in the 10000K XM also had thicker plates... so there is certainly an obvious difference in growth due to intensity....
But im still not sure that spectrum choice does not have an effect on pigmentation (Im not talking about the apparent color while observing under blue vs white light)
what do you think.... does spectrum choice have an effect on true pigmentation (not observed apparent coloration due to lighting choice)?

 

[reefnut]

I think your observation is a good one!! I don't think anything has changed in my tank other than lighting but in no way is it a "controlled" experiment.
I'm undecided if spectrum has a effect on pigments. I do believe intensity has a effect but going from a 10k to a 20k... I'm not sure. I have not seen it in my tank yet??
IMO, again... PAR is the key. The zooxanthellae can utilize lighting at a wide spectrum for photosynthesis... the 10k bulbs produce a higher PAR than 20k bulbs.
Also, 10k bulbs do have a good amount of the blue spectrum. If you look at a spectrum chart they do produce the blue spectrum, they just also produce all the other spectrums as well.

 

[hurt]

"This is what I read... "The extra watts from actinics really do not buy you much in the way of helping out corals as the spectrum of actinic light is not enough to make much of a difference." and I agree with that 100%."
Again, I don't see how you can possibley think that actinics do not make a difference in coral growth and coloration. True actinic's in the blue spectrum are the last spectrum to be filtered out which makes it the deepest penetrating spectrum into H2O. I am just speaking of personal experience when I will only turn on my VHO actinics and not my MH's for a day. When I only run my actinic's my corals and anemomes show excellent polyp extension and great color. This is the main reason I can't understand why you think they have no effect. Obviously they are responding to the spectrum of light.
10k's have far greater par than 20k's. This is why 10k's will grow corals faster. 20k's however are more in the blue spectrum and this is why I feel they seem to produce greater coloration in corals.
http://www.cnidarianreef.com/lamps.cfm
A 250W MH XM 10K bulb on an IC 250 MH ballast produces 530 par
A 250W MH XM 20K bulb on an IC 250 MH ballast produces only 270 par

 

[shawnhardy]

Originally posted by NM reef
In part your question seems to be why use 10K MH's along with actinic suppliments instead of just using 20K MH's without actinics.....


This is my original question. I knew there was more to it though...as I am learning through this discussion.
So the PARs are pretty much cut in half on 20,000K bulbs. Sounds like 2x150 MH 10K and supplemental actinics is better than 2x250 MH 20K.

 

[hurt]

I am assuming the 2x150's are HQI's DE. HQI bulbs put out more par than they are rated to, that's a good thing. I run 2 250watt XM 10k's along with 2 110 VHO super actinc's on my 55 and couldn't be happier. If I were you I'd go with the 2 150w HQI MH's along with VHO actincs. I personally have noticed a big difference in my corals after switching from PC actinics to VHO actinics.

 

[sammiefish]

just another comment...
dont forget, more than enough is a waste... even if it is a bulb with a better PAR rating.

 

[shawnhardy]

Yes, I am talking about HQI bulbs. From what I have heard/read, they seem to be better then the mogul bulbs right?
Not sure I know what you mean sammiefish...

 

[reefnut]

Again, I don't see how you can possible think that actinics do not make a difference in coral growth and coloration. True actinic's in the blue spectrum are the last spectrum to be filtered out which makes it the deepest penetrating spectrum into H2O.
The blue spectrum is the deepest penetrating spectrum but our tanks are only 24" deep or so. There is not very much spectrum lost in 24" of water.
Now, please read the post for what it says, I pretty sure this is what TheGrog was saying which I fully agree with...
"The extra watts from actinics really do not buy you much in the way of helping out corals as the spectrum of actinic light is not enough to make much of a difference."
Actinics do add usable light (PAR) so they do benefit the corals to an extent BUT when you are running MHs the benefit from the actinics is minimal. In other words, the MHs are producing all the light the corals need... so adding additional light is just for appearance.