light for tall skinny tank

[LeeR]

hey im new here and i am making a tank that measures 12"X 21"X 12" (l X H X W) its also got a built in overflow/sump in the back.. anyways.. i need to figure out lighting and i dont really want to go the metal halide way because of money. so i was thinking of using the 12"coralife aqualight 2X18w.. do you think this will be enough so suport some type of soft corals

thanks