What is the proper wattage for a 20 gallon saltwater tank?

Answer 1

Plan on 2-5 watts per gallon depending on the lighting needs of any live plants you plan to keep: http://www.fishlore.com/aquarium_light.htm

OOps! I just reread you question and saw you asked about saltwater. That makes a difference! If you are keeping only fish & nonphotosynthetic inverts, the answer would be the same as far as wattage. But now you have color spectrum to consider. Most saltwater species do well under 10,000K bulbs for a regular fluorescent. Some folks like the color better when a 3% actininc bulb (bluish light) is added. If you only have a single fixture, you can get a 50/50, which combines both spectra. If you have a double tube fixture, you can get 2 50/50, a 10,000K and an actinic, or a 10,000 K and a 50/50.

If you're going to get into corals, clams, or anemones with photosynthetic algae, you'll need something stronger, either a VHO (very high output) fluorescent or a compact fluorescent. On my 20 and 29 saltwater tanks I run a double compact fluorescent (Lunar Aqualight) with a 65w 10,000K and a 65w 3% actinic by Coralife (130 watts total). It also has two blue LED lights for a "moonlight" effect.

(my light system):
http://www.thatpetplace.com/pet/product/productInfo.web?picGroupKey=10940

other systems available:
http://www.thatpetplace.com/pet/product/categoryInfo.web?options.passInCategoryKey=22943

Hope this helps!

Answer 2

When you say wattage? Do you mean a 110 line? Do you mean the lighting (depends on what you have in it)

Do you mean how many plugs will you need to run one with filter, power head etc? More info please