What's the truth about Power Compacts?

[dufreneh]

I'm about to start setting up a 90 gal tank. After starting it as a FOWLR tank, I will eventually make it a reef tank. I was reading "The Simple Guide to Marine Aquariums" last night which kind of confused me. From the book:

"A 55-Watt PC actually provides more light intensity than a 110-Watt VHO. Needless to say, when using power compacts, the 3 to 5 Watt-per-gallon rule does not apply."

According to this, I can have less wattage and more light with power compacts. A 4x96w fixture for my 90 gal is almost double the price of a 4x65w. If this is true, I could save a lot of $$$, but I figured I would ask a trusted source such as AA first.

 

[captivereefs]

The first thing is you need to decide the corals you want to keep. This will help alot in light selection. PC'S are nice but they are not for every situation or coral. I like them for softies and most LPS corals but not for SPS or clams.


Do not go by watts per gallon as a way to determine proper lighting over a reef. The light source dictates the intensity not the water volume!

 

[malkore]

Listen to captive reefs on this one.

The main reason though, is that wattage is NOT a measure of intensity...it's a measure of electricity USED to produce the light. Lumens is more useful measurement of light output.
Different light bulbs have different watts to lumens ratios. Incandescents suck, metal halides are better, then flourescents, then VHO, then PC.
metal halides are still nice though because they just put out soo much light in a tighter area, and allow you to supplement with actinics to add even more intensity.

hope that shed some light on why wattage isn't a great way to measure things.

 

[dufreneh]

Thanks for the help. I think I'll go with the PC 4x65 type of fixture. At least for the first year or so, I'll be keeping fish, live rock and inverts. I will be building my own canopy so if I decide to get SPS, I'll add some MH bulbs later. No problem because I'll be taking my time with this anyway.

 

[boardsurfer]

Down with LSU!

 

[fishfreek]

Also note while some belive a 55W puts out more light than a 110W the 55W will only light a 2' long portion of the tank where a 110W will light a 4' portion.

I have 4 X 110W VHO over my 75 and I can tell you I would NOT get as much light output if I had 4 55W PC's. How do I know. Because I used to have a pair of 55W PC's over a 20gal tank. So I have some reference. I also have 4 X 96W PC over an 80gal tank and the corals grow faster in the 75 than the 80 even though if a 55W PC puts out more light than a 110W VHO you would think a 96W PC would then most definatly put out more light than a 110W VHO.

I belive the real measure of light output is lux.

 

[dufreneh]

Thanks fishfreek. I'll keep that in mind.

Seems like boardsurfer is confused with a Gergia avatar and a location of South Carolina.