Calculate your watts per square foot rather than watts per gallon,
for example for 3 square feet of tank, a tank 12 inches by 36 inches long,you need minimum 50 watt per square foot for lps and higher light corals.Thus, 50 x 3= 150 watts of light needed over the tank. For all sps coral tank: 100watt per square foot. For your condy anenome, you need minimum 75 watt per square foot.
Mushrooms, zoas, and lower light coral can be kept at 30 watt per square foot.