Lighting gurus: BLV's 20KK real?

[narkosis]

Hi AT, Tanzy, other lighting-obsessed guys,

I notice that in many online stores and even some LFSs, there's a bulb from BLV from 150W to 400W that's sold as a 20KK bulb. However, as far as I can tell, BLV never has and doesn't make a 20KK bulb. They do however, make coloured bulbs in red, green, blue and magenta. Unfortunately, these are largely monochromatic , and not full spectrum and thus not terribly beneficial for the photosynthetics that need the light. I think this is why these coloured bulbs are considerably cheaper than the Radiums or Saki 20KKs.

Have any of you guys tried these bulbs and found them beneficial or somewhat lacking in some way?

Cheers

(deep_end)

P.S. How come there is a Warn indicator below my name in the threads? Am I being too quiet?

[Achilles Tang]

Your warn indicator is at 0%. Nothing to worry about.

You can mostly ignore the k ratings of the blue bulbs.

The Ushio Blue is just that... a Blue MH. They can stick a k rating to it as 20,000k if they want as most peaks are in the blue spectrum anyway... the most important thing is to make sure the right peaks at 420 - 450nm is there and that the PAR from these Blue MH bulbs are high enough to support photosynthesis.

Being monochromatic is a feature of the blue bulbs. You can't expect full spectrum unless you go <10k bulbs.

The problem with most of these Blue MH bulbs is finding out their spectral charts.

My 2 cents,

AT

[andysho]

i am using BLV 250w 20k for my 2 feet cube tank

look great so far

[narkosis]

But if its monochromatic, I don't think the spectral charts are going to do much good. From what I gather about colours, the main reason a bulb's output appears blue is due to the relative high peaks of 420-440nm compared to the other colours. And if this is the case, PAR from the greens and yellows would be reduced, no?

[narkosis]

i am using BLV 250w 20k for my 2 feet cube tank

look great so far

Yeah, I know. I've seen them light up buildings and the colour is absolutely awesome. But aesthetics aside, how does the BLV "20KK" pit itself against something like the Radiums?

[Tanzy]

I prefer the BLV Blue over the Radium. Cheaper too. The Radium might be less blue depending on what ballast you are using. I think the BLV Blue are pretty good companions to 6500K or even 10000K bulbs.

[Achilles Tang]

The Radium is also a blue bulb but an energy saver version.... so its not really a true 400w bulb. (i am talking abt the 400w version here).

As Tanzy says... it depends on the ballasts... it may be overdriven a lot with e-ballasts, esp. good ones like the Blueline e-ballasts.

When overdriven, they emit a much whiter light but their lifespan also falls greatly.

I think a lot of people are moving away from Radiums now.

[ben]

the real photosynthesis uses is the blue spectrum at 420nm to 450nm. Nobody can tell u the exact value. other lighting spectrum is actually not helping photosyntesis but instead looking nicer form our eyes. I have forgotten which website I have read this but if u want to knopw, u look for it.

[Achilles Tang]

Not entirely true. Photosynthesis happens in the lower spectrum ranges as well.

If going by this assumption, there is no logic why a 6500k bulb will induce faster coral growth vs a 20k bulb as there is as much blue light coming from a 6500k (just that we don't perceive it because of the stronger red, yellow & green spectral spikes).

Some corals do utilize different spectrums of light for photosynthesis and not just the 420 to 450nm spectrum.

Full spectrum bulbs are the best, unfortunately, they look awful to our human eyes.

[narkosis]

Full spectrum bulbs are the best, unfortunately, they look awful to our human eyes.

Gotcha boss. So this sort of implies that the blue tubes in the market can still be used, within reason, for certain corals, even with a much reduced PAR from the non-blue frequencies.

The actual reason for my thread was to determine whether I should carry only bulbs with a balanced spectrum and a blue spike or those with a huge blue spike and minimal everything else.

Thanks

[Achilles Tang]

Hmmm.... you ought to sell both.

The blue MH bulbs not only serve to blend with the lower k bulbs for a whiter look but on their own, can also induce nicer colours to 'pop' from certain corals.

They do cause corals to flourescence.... so it does give a bit of 'actinic'-like effect to the reef tank.

I like the look of my tank with just Blue MH bulbs... certain colours jump out very well!

[fecgoh]

You guys can get information here:

http://www.blv-licht.de/redsys/prod/showPr...pid=2&prodid=17

Click on the Adobe Acrobat file on the right. Most of the information you need is there. The spectral distribution for the BLV 150w 20k is on the 3rd page. It have a strong peak at 450nm typical of 20k bulb.

Hope this helps.

Frankie

[narkosis]

Frankie,

Thanks a lot for the SD chart. Was looking for it high and low. From the chart, it appears that the other wavelengths are rather too subdued to be beneficial for photosynthesis. But as AT pointed out, it can still serve to bring out the fluorescence in corals, so in all likelihood, I will probably carry them.

Roger