How many watts should you have per gallon of water in your SW Fish Tank?

Question

I'm thinking about getting some coral.

Answer 1

I addition to what Copperhead said, please keep in mind that watts per gallon depends on many factors (and is a somewhat archaic term IMO).
Many modern lights do not have the same lumen output per watt generally you want a lumen output of over 60 lumens per watt.
The newer high end LED lights are an example of poor lumens per watt (they are improving though and this statement of mine will hopefully be incorrect soon)

The newer T-5 and newer yet T-2 lights have excellent lumen per watt output.

The VHO and SHO are other excellent choices as per lumens per watt, and of coarse MH are generally the "kings" of this parameter.

Other important factors include Nanometers, Kelvin (heat output).
As already stated 420 Nanometer actinic combined with a 10,000 K daylight bulb is a good starting point.
I prefer to use VHO for basic reef tanks and then add Metal Halide for advanced reefs (hard corals, clams)

I have also used 6400 K SHO and T-2s for marine tanks to aid in photosynthesis since this is Kelvin range that generally supports the best PAR (Photosynthetically Active Radiation)

For MUCH more up to date Aquarium lighting information, please read this article:
http://www.americanaquariumproducts.com/Aquarium_Lighting.html

:~) C

Answer 2

I'd go with at least 3 WPG. That will take care of most of the photosynthetic coral, but a lot will still depend on tank depth, water clarity, position of corals in the tank, etc. You'll also need to have the lighting in the correct wavelengths/color that the corals can use for photosynthesis. I generally use 1/2 of the lighting in 10,000K and 1/2 in 03 actinic or a 50/50 10,000K/03 actinic

If you just have a standard lighting fixture, it would be better to upgrade to a compact fluorescent, T-5, HQI, or metal halide system.