Dark Areas

[Jaymeany]

I have heard some talk about dark areas in a tank. Obviously this affects your watt/gallon, but I like the idea that there is an area that allows for some darkness. Is it feasable to figure out your watts/gallon based on each side of the tank? I.E. for a 75 gallon tank figure out the watt/gallon for 37.5 gallons for one side (well less due to live rock adn sand displacement) and a seperate value for the other side. What are peoples' thoughts about dark areas in tanks?

[tendar]

Watts per gallon is not really that effective. It more goes towards the corals you plan to keep and the light they do best under. A pair of power compacts or setup of VHO bulbs over any tank 24" tall or shorter tank will support most all softies and lps that are under them and sps and clams pretty much need metal halides to get good growth and colors. You can keep sps under power compacts and vho but will not get the colors or growth.
Plus some thing like you said in that if you only light part of your tank the watts per gallon goes out the window also. Say you have a 180 gall tank but only run 2 250 halides. The watts per gallon looks bad at 2.77 wpg but you can easilly keep sps and clams as long as they are in the the 2ft by 2ft area that each of the halides cover.