Whats the deal with HID metal Halide lamps?

[mjweber]

Was browsing through my new catalog of expensive aquarium equipment and I came across this new kind of MH Light that uses a HID metal halide lamp. The bulb looks completely different. Has anyone had any experience with this new lighting technology. I know its not totally new, since it is a MH but i'm just curious.
Also I work in a lab that has an instrument which uses a xenon bulb, for reading biochemical assays. This bulb covers a very large spectrum, since the light is diffracted and used at specific wavelengths by the instrument to excite certain florescent labels. Has anyone ever thought of using one of these bulbs to light a tank, I know that the one we use appears MUCH brighter and purer white than a MH. Just curious if its been done.

 

[scsinet]

These lamps are the same old metal halide technology, they just use a form factor that is not commonly available (perhaps yet) in the trade.
I wouldn't be worried about these, just make sure you have a source for replacement lamps before you buy. Most major lamp manufacturers aren't making these yet, so to say the least, your options for replacements will be limited.
As for the xenon lamp, it's probably a short arc lamp. Arc lamps produce light all across the spectrum. The trick with aquariums is to maximize the PAR (Photosynthetically Active/Available Radiation) that is useful to the livestock, yet minimize the other wavelengths that contributes to excessive algae growth. So keeping that in mind, you can see that throwing all wide spectrum light into the tank will probably cause more algae growth than you want. Sure, you can use filters like your instrument uses, but then everything that is filtered out contributes to wasted light, wasted energy, and needless heat.
Other disadvantages are that arc lamps are VERY expensive (usually starting at hundreds per lamp), have a VERY short lifespan (to the tune of tens to low hundreds of hours), and give off more heat than you want to contend with.
So people may have thought of it, but I doubt it's worth it.

 

[rileybb]

i have a fixture like the one above different make and it takes these they are great and you can get replacments for them easy online....the only difference with HQI they are stronger then just metal halid they have uv i think so you need to have a glass cover or they can burn up your corls...someone please correct me if im wrong