metal halide question

[shavo]

does anybody know if there is a relationship between the different ratings on metal halide bulbs and algea growth?

Orca asked me this question and I thought it was a good one, does 10 K white bulbs produce more algea than a 20 K blue? just curious

and is there a difference if I was to keep clams? do they prefer a certain light to another? does it make any difference even if it is still the same wattage?

thanks

 

[Anonymous]

there is a tale about lower temperature get you more algae. Certainly the coral have have different "natural" temperature. More specifically, the deeper coral have a higher kelvin temperature due to the extra water on top of it. It is very different from those near the tidal zone.

But does lower kelvin *grow* more algae? I don't know if anyone want to answer that directly. I would just say that in a reef tank, the limiting factor for undesireable algae is not the light. nutrient is a far more important issue.

Clam is the same. T. crocea usually live in a slightly lower K light condition than, says, T. gigas.

IMHO, you just pick the light that make the tank look best to your eye. Just make sure it is efficient and won't give off to much heat like those halogen lamp.

 

[ChrisRD]

Something else to consider, beyond just the spectral differences - in general, whiter lamps tend to emit more PAR than bluer lamps of similar style/wattage. More light with the same nutrient levels = more algae (to a point, however, it also means more growth for the target animals as well). This alone may account for the idea that 10K lamps promote more algae growth.

I agree with the idea that you should light the tank however you prefer (as long as you're providing enough light for your animals) and then control algae problems by controlling nutrient levels. That said, personally I've had better coral health/growth under broader spectrum "daylight" type lamps as opposed to more monochromatic blue lamps.

 

[mr_X]

what is PAR?

 

[shavo]

very interesting, so in your opinion, i personally like the 14K to the 10 K for the "look" of my tank. but would it be better to have the 10 K lamp as opposed to the 14K lamp if I wanted to keep a healthier clam?

also what is PAR???

 

[danmhippo]

what is PAR?

If you are really anxious to know, you can read this

http://www.aquabotanic.com/lightcompare.htm

The standard measure that quantifies the energy available for photosynthesis is "Photosynthetic Active Radiation" (aka "Photosynthetic Available Radiation") or PAR. Contrary to the lumen measure that takes into account the human eye response, PAR is an unweighted measure. It accounts with equal weight for all the output a light source emits in the wavelength range between 400 and 700 nm. PAR also differs from the lumen in the fact that it is not a direct measure of energy. It is expressed in "number of photons per second", whose relationship with "energy per second" (power) is intermediated by the spectral curve of the light source. One cannot be directly converted into the other without the spectral curve.

 

[mr_X]

i have to get one of those light meters to measure PAR. meanwhile, if i read that correctly, metal halide happens to be one of the better sources of light. i was wondering if my cheapo bulbs were sub-standard, but from this article, i gathered that i have plenty of PAR for my application either way. :wink:

 

[mr_X]

what does everyone think of this statement?:
14k--The most popular metal halide color temperature available. Duplicates the coloration of the mid-day tropical sun between eight and fifteen feet of water depth. The perfect color temperature for replicating the natural light for the majority of reef inhabitants. Provides a white-blue full spectrum light that brings out the colors of the reef and it's inhabitants, while producing a crisp, shimmering effect throughout the aquarium. Ideal for shallow and mid-range reef animals. Appearance: Blue/White

 

[ChrisRD]

Like many things in the hobby - it's a load of marketing BS. I would just buy whatever you like provided it's bright enough to keep the animals you want to keep.

The truth is, there's probably not a single 10K, 14K or 20K halide in the hobby that does a good job of simulating a natural underwater light field. In fact, Sanjay did an article on this a while back and IIRC the Iwasaki 6500K was the closest approximation.

http://www.advancedaquarist.com/2005/8/ ... hterm=None

HTH

 

[shavo]

i just bought 6 metal halide bulbs direct from china, is there really a difference in name brands? I see bulbs for 50-60 dollars. I bought bulbs for 10 dollars directly from china, plus 7 dollars shipping. they are 14K

I am happy with the purchase

 

[mr_X]

chris just answered that shavo

 

[shavo]

Yo X, no he didn't I know your all about econo shopping but I was asking about brand names not colors. Read my questions fully before you decide to correct people on here. So is there a real difference if I bought a bulb direct from china not a specific name brand, or is there a real difference in the kowasaki utishi or whatever they call it.

 

[ChrisRD]

Some people report problems with longevity or premature spectral shift with cheap lamps. You very rarely hear these complaints with the quality brands.

At that price point I wouldn't be surprised if you had some issues, but then again, the lamps are so cheap it might still be worth it to you. Will you have enough trouble with the cheap lamps to justify the higher price of the reputable brands? Tough to say - only time will tell.

My experience has mostly been with the better known brands like Ushio, BLV, AB, etc. I've never had a single problem lamp with those companies. The only cheaper lamps I've tried were a set of Coralvues (made in China) and they had noticeably shorter life and lower output than the other brands.

JME