PC versus MH

[mineralrock]

here's what i guess I never understood.

 

say you have a 70W halide and a 96W PC....which would you put on a ten gallon tank? Are halides superior because of the higher spectrum or is it simply a matter of wattage?

[Undertheradar]

you hinted at it pretty well there....halides are superior due to better spectrum. The same tank that I once had a 96watt over required a 12hour photoperiod and wasnt really doing that great...at least in comparison to how it was as soon as I swapped out the light for a 70wattDE. The corals have all 'taken-off', and under just an 8 hour a day photoperiod, so Im saving on electricity as well!!!

[mineralrock]

hmmm oh well...I'm stuck with the 96 for now.

[ninhsavestheday]

96 would be fine as long as you dont keep any SPS or clams.

[bobioden]

How is the green mandrian doing? What kind of foods is he eating?

 

???

[Aiptasia]

It's not so much the wattage or the spectrum, it's the intensity of the light. HID lighting (mercury quartz iodide and Metal Halide lights) put out far more intense light than any type of florescent tube.

 

Florescents put out diffuse light at equal levels from all parts of the tube, whereas metal halides put out bright intense light that can reach deep down into water.

 

Therefore, their applications are going to depend largely on how intense you want the light over your corals and how deep the light has to go to reach corals at the bottom of your tank. Since florescent light is so diffuse, the PAR (photosynthetically available radiation) is roughly 50% less than at the surface of the bulb at just 1 foot away, and practically nil at just two feet from the bulb.

 

With MH bulbs, you have less dropoff in PAR values because of the intensity. Their PAR values can reach down to four to five feet from the surface of the bulb. Therefore, they're much more desireable bulbs for deeper, larger tanks with more water volume or for high intensity applications, such as maxxima clams or neon colored top water SPS corals.

 

Both lamps have their good and bad issues. Florescents don't put out as much heat (less water evaporation) but they can't be used over a deep tank. The light spectrum and light output levels drop the moment you use any bulb, but florescents need replacement more often (every 6 months) than MH bulbs (every year). Florescents are easier to fine tune to specific wavelengths of light than MH bulbs, so creating combinations of different bulbs at different wavelengths/color temperatures is easier with florescent tubes. In fact, most aquarists will use supplimental florescent light (actinic 03's, etc.) in conjunction with their MH bulbs to create a better overall quality of reef light.

 

And,

 

You can keep clams and SPS corals under a 96w. 50/50 bulbed florescent appliance as long as it's a fairly shallow depth (18" or less) and it's the right kind of SPS coral/clam.

 

I have squamosa and blue lined derasa clams under my 130w. coralife lights and they're doing fine. I also keep orange monti, pink pocelliopora, green staghorn and green monti under them with no problems. They're growing fine. The clams have about doubled in size inside of three months time and the staghorn is ready for fragging (maybe by next weekend i'll have the time).