460 nm vs 420 nm

[Anonymous]

Have you looked at Ceramic Metal Halides?

Some of them offer a comparatively even spectrum:

Here is a graph comparing a Phipps MasterColor CMH to HPS http://www.growlightexpress.com/images/cmhvshps.jpg

What I don't like about sulfur plasma bulbs is the huge green spike.

I have indeed, but they're still MH with peaks and valleys just like every other bulb. I could get over the green "peak" (it's so smooth it's hard to call it a peak) in the SP bulb's spectrum if they'd sell it to me for a reasonable price. I haven't actually seen how much power these things consume, that's another consideration I must keep in mind.

 

[Chopper Greg]

I'm not so sure. :|

I can live with some spikes as long as the critical wavelengths are there and if the CRI is decent, and sulfur bulbs have anything but a decent CRI.

When used in commercial applications the green tint has caused repeated customer complaints, and while bulb life is decent, it is dependent on the rest of the equipment doing it's job. Should the cooling fail ( and apparently it does with enough frequency to cause reliability issues ) the hot sulfur then eats through the glass. Magnetron life expectancy is around 6 months and then you have to buy an expensive part of the equipment.

Other things to consider - if a full spectrum is important to coral health, then the sulfur bulbs not only lacking with both the IR and UV ends of the spectrum but a large part of the red and blue parts of the spectrum ( indeed compared to sunlight it have very little violet ) - while the lack of IR is not likely to be an issue, we know that at least some corals make use of some UV through color shifting. We also know that some studies have shown that terrestrial plants rely on some UV light for best photosyntheses ( chloroplast under full spectrum sunlight are more active while chloroplast under sunlight that has the UV filtered out are less active and may even be hindered ). Yes I know that water filters UV, but I I can not help but think that corals ( especially those from shallow waters that would be normally exposed to at least some UV ) would probably have issues by an almost total lack of UV and reduced levels of light in almost everything but green -indeed, I have been considering about the possible use of low power UV-A ( with a peak of 360-370 nm ) bulbs as a possible alternative to actinic bulbs.

 

[Anonymous]

So you think that even sulfur plasma would need some sort of supplementation, yes? Since $$ is a primary consideration, if it's really using that much of its energy to make green light (curious to know PAR/PUR of the thing, because that's what I'm really after here) and that light isn't being utilized then that's a waste.

Hmm. Well, this has evolved somewhat from the actinic question in an interesting fashion.

 

[Anonymous]

Wasn't there a tongue in cheek article AA did showing that red light was basically useless for growing corals? Seems to me if I can remove that part of the spectrum that the corals don't actually use then all the better. I mean yeah they have the Sun... shining through X meters of water, but that doesn't mean it uses all or even most of the Sun.

 

[Chopper Greg]

So you think that even sulfur plasma would need some sort of supplementation, yes?

To a very real degree, "Yes".

Since $$ is a primary consideration, if it's really using that much of its energy to make green light (curious to know PAR/PUR of the thing, because that's what I'm really after here) and that light isn't being utilized then that's a waste.

That is ( an excessive amount of light in one part of the spectrum ) something that I have always had a problem with while researching lights for greenhouse use, and the reason I have always disliked about HPS lights.

In my research of greenhouse lighting, one thing I have become convinced of is that just because a light source puts out a lot of photons, it doesn't necessarily mean that plants ( and other organisms ) can make the best use of them.

The reason that most terrestrial plants are green ( or to us look green ) is because that is the part of the spectrum that they make little to no use of and so the 'green' part of the spectrum is reflected.

Based on the heavy green cast of the sulfur bulb, I would have to judge it as being next to useless in a plant growing situation - it is for this very reason that experiments are underway to improve the spectral emission of sulfur bulbs to increase it's plant growing ability. OTOH, judging by the way that it seams to keep coming and going and the fact that at least 3 companies that were making them, have gone out of business, I suspect that they will remain more of a tool for general purpose lighting than a specialty lighting tool that is required by reefs.

Any excessive green, will make corals with red coloring, seam dull and muted - in fact enough green light and not enough red light will make anything in the tank with red coloring come out brown or even black.

Perhaps it's just me, but I prefer to see things as close to true color as I possibly can, and that is why I am going to be basing my light selections based on CRI as much as anything else.

Hmm. Well, this has evolved somewhat from the actinic question in an interesting fashion.

Yes and no.

I see it as more of a continuation of the 460 / 420 issue, as the type of lighting chosen will directly impact this debate, either as a part of being the problem or the solution.

Wasn't there a tongue in cheek article AA did showing that red light was basically useless for growing corals? Seems to me if I can remove that part of the spectrum that the corals don't actually use then all the better. I mean yeah they have the Sun... shining through X meters of water, but that doesn't mean it uses all or even most of the Sun.

I couldn't say, but consider that since seeing the colors in that part of the spectrum from out side of the tank, requires the presence of light in that part of the spectrum you would probably achieve the look of actually being at the depth in which there is no red - that is to say you would be self imposing a type of color blindness on your self when viewing your tank if there was no red light available. This might be alright for some people, but I want to see all the colors that are there to be seen, and that requires the entire visible spectrum ( or if not the entire spectrum, a high enough CRI to make it appear as if the entire spectrum is there ) and some of the invisible spectrum as well, because of the color shift that some corals do seam to be able to accomplish.

So while the corals may not be making use of the red part of the spectrum, anyone who views the corals, will be using it.