high pressure sodium light

[nathan_unsane]

I am wondering the differance (besides price) between an aquarium halide light, and a hydro-ponic grow light, or a parking lot lamp?

I am aware of lumens and wattage, i have a sodium high pressure 100 watt light, i wondering if this will suffice my 37 gallon tank. For coral and fish that is...

There are dozons of specs on a G.E. website, which mean nothing to a neophyte such as myself... Ive copied some, may be some use to a person with knowlege on the subject...

Pulsearc Multi-Vapor Metal Halide Lamps
Product Code 18680
Description MXR100/U/MED
Watts 100
Lumens (Initial) 9000
Lumens (Mean) 6200
Average Life in Hours 15000
Color Temperature (K) 3200
Color Rendering Index (Ra) CRI (> or =) 70
Operating Position Code U
Fixture Type - Open/Enclosed E
Bulb Type BD17
Base Type Med
Max Overall Length (In.) 5.43
Max Overall Length (mm) 138.000
LCL (In.) 3.43
ANSI Ballast Type M90
Sales Unit UPC 043168186803
Case UPC 043168186803
SCC 00043168186803
Govt. Nat'l Stock Number 6240013506808
Case Quantity 6
Additional Information Clear
Volts 100


thanx if anybody can help

[goby1]

Those specs are for a metal halide, not high pressure sodium bulb. I'd suspect that the lumens would be higher for the hps, with a significantly lower cri. First off, aquarium specimens would look awful under an hps bulb. Though the lumens and par might be higher, to guess their sheer efficacy you'd have to know more about the photosynthetic absorption of the algaes that grow on our corals. Chlorophyll utilizes light in the red region, and hps have a lot of this, which is why industrial greenhouses often use them as supplemental lighting. Blue light can have an effect on plants, but if I remember correctly it is not through photosynthesis. The only experiments I know of for corals involve absolute absorption - not that specifically utilized for the synthesis of sugars. Lumens are units which consider the human eye's sensitivity to the middle of the visible spectrum, or green, and par is normalized to the fact that shorter wavelengths carry more energy per photon. Par also only includes 400-700nm, which is the visible portion of the spectrum. "Photosynthetically active radiation" is a misnomer. It should be more like "possibly photosynthetically active radiation." If the term were applied to plants, then it would obviously be heavily flawed, as it does not take into account chlorophyl's sensitivity to red light. I don't know how the corals' algae respond to different wavelengths in terms of photosynthesis or other processes that are important. The other test to do you be to use the hps bulbs and find out.

Remember, you will only see a certain color in the tank if 1.), it is being illuminated with that color, and 2.), if that coral or its algae either reflect or re-emit that color. There are lots of brown/yellows in our tanks, which is why it is hard to find lighting that will make them look good. Overstimulating the blues can detract from the yellows.

The factors that are important for us are the absorption of light for photosynthesis, the absorption of light for other processes (???), and making the tank look good. The first two are complicated and I've never seen a good study of this (but haven't looked hard either).

G1

[nathan_unsane]

thanx for the insight...

do you know anything about the bulb listed in the specs, and if that is sufficent enough?

and have you heard of the tangent blub? i'm not sure if it even exists, the local fish store was explaining it to me unclear.

[goby1]

The initial lumens/watt is 90. That is similar to most aquarium mh bulbs. But the cri is lower than 10kK bulbs, at least. Why are you not interested in traditional aquarium bulbs?

Don't know of a tangent bulb. I think that bulb will work fine, but it won't look that good (3kK color temp). Also, you should note that color temperature does not rigorously apply to fluorescent and mh bulbs, that have outputs with discrete spikes at several different wavelengths. Color temperature refers to the temperature that a material (specifically an ideal blackbody radiator, which most metals will mimic when very hot) will be at when it emits with a peak at one wavelength, with a specific equation describing the way that the intensity drops off on either side of the peak. Incandescent bulbs are much more aptly described by color temperature.

G1

[nathan_unsane]

i'm trying to get away with using the bulbs and ballasts i used for hydroponic growing system...

i also have a 400 watt metal hilide but it's so hot, bright and uses alot of power

will the low color temp promote bad algee growth and/or starve the coral, or is the bad appreance of the hobbiest the only flaw?

can i compinsate with one or two fluorescent bulbs

[DrBDC]

Isn't there a mh aquarium bulb that runs on a hps ballast?

[goby1]

I think that color temperature affecting algae growth is a myth. I don't know how the corals' algae photosynthesize, nor what other processes are important for corals' algae to grow correctly. Horticultural hps bulbs are designed to output in the region where chlorophyll converts light to sugars. I'm guessing that corals' symbiotic algae do not have chlorophyll because they are not always green, but I could be dead wrong there. Again, the specs you provided are for a mh bulb, and you mention you have an hps bulb. What organisms are you trying to keep? What is the ballast for the 100? The 400? 400 is generally not needed for a 37 gallon tank.

Why do you want to have a saltwater aquarium if you don't care how it looks? If you're skimping on lighting because of cost, how do you intend to create the other tanks parameters that are needed for a healthy system?

The hps will make the tank look like a vat of mustard. It will certainly grow phytoplankton and macroalgaes very efficiently.

G1

[xtrstangx]

Color Temperature (K) 3200

That will look like someone peed in your tank.

You want a kelvin rating of 10,000 to 20,000. Plus, algae will grow much better at lower kelvins as they prefer the red spectrum more.

[nathan_unsane]

i just don't have the money to invest in a 400 dollar lighting system and i understand there are corals that can survive in lower lighting aquariums...

i've hooked the light up and it seems to have a blue(er) glow after the bulb stays on, and doesn't look any worse in the water reflections then the 12' florecent

but i don't want to waste money on coral and have it not make it, are feather dusters a type of coral?