Soft Coral light requirments

[NoSump]

I have noticed that there are a good deal of soft corals that reportedly only require small to medium lighting.

I purchased a 4/96 watt pc unit (with a moonlight) for a 72 gallon tank. Although, I understand that MH is really the best lighting, I chose to avoid the expense, bulkiness, and heat generation of MH. I had read that PC generates twice the intensity of VHO. My theory is/was that my set-up should provide some flexibility in my reefing choices (but may not be able to support clams or high light requirment anenomes).

My question is this: If I start out with only low to moderate lights requiring softies, can I get away with operating my light unit with only 2 96 watt bulbs (one 10K and one blue actinic), in order to conserve bulb life and limit heat while still matching needs? Also, my light unit will be mounted 13" from the water surface - is that too far? Thank you

[Ninong]

I wouldn't mount PC lamps 13" from the water. They can, and should, be mounted closer for maximum effectiveness and efficiency. If we are talking about just PC lamps by themselves, I see no reason to mount them more than 4" above the water unless you run into heat issues.

I wouldn't believe the claim that "PC generates twice the intensity of VHO." That seems overstated, if you ask me. I do not believe that a 96w PC lamp generates twice the intensity of a 95w VHO lamp. The only measurement that counts is the quantity and quality of the light incident on the particular coral surface. You can measure that in PAR with an Apogee PAR meter (~$400) or you can simply measure the lux with an inexpensive luxmeter (~$100).

You can keep a wide variety of corals under your proposed lighting provided you exercise judgment in their placement. You can probably keep certain host sea anemones, too, provided you feed them regularly. Whether you can keep Tridacna clams or not is open to debate. The question then becomes one of what is ideal vs. what might work. There is not much doubt that high light intensity is required to maintain the brilliant mantle coloration of electric grade T. crocea and ultra grade T. maxima but some people do keep clams in tanks without metal halides. T. derasa requires less light than T. crocea or T. maxima and you might be able to keep one of those since your tank is relatively shallow. Daniel Knop, a popular authority on Tridacna clams, recommends a minimum of 250w metal halide lighting as ideal for all species, but many people seem to get by with less than that.

[Poseidon]

I don't think you would see a sustantial difference in your electric bill over a months time. As far as heat is concerned I had a 4x55 Phazer IV sitting ON THE GLASS tops of my 55 and did not have any trouble. I think you should be fine...

[NoSump]

Thanks guys. The reason for the 13" gap is that I purchased an acqualight unit that exactly matches the length of my tank. My cap also matches the length of the tank - therefore, the only option that I could come up with (if I want to use the cap) is to mount the lighting unit on top of the cap. That's were my 13" gap comes from. If it really degrades my lighting, I may be forced to mount the unit on top of the tank and forego the cap. I guess it will come down to asthetics vs. effectivness.

[Poseidon]

In my book, form ALWAYS follows function!