I have 3watts per gallon and am doing nicely, mushrooms, xenia, green star polyps, and caulestria. All look great except the caulestria, it has it's good days and bad. My setup is 42 gallon hex, 24" in height. The mushrooms thrive on the bottom of the tank, the caulestria is about 3/4 to the surface, green stars are bottom and middle doing nicely, really thriving. The xenia is in the top one third and reproducing like crazy. Water quality is just as important as light to corals. Good water quality and 3watts/gallon is doable for lots of soft polyps which can be quite diverse in appearance.