One 40 watt bulb over a 75 gallon tank is just almost bright enough for your fish to see where they are going. This is not going to sustain any corals. You may have luck with feather dusters, urchins, starfish, shrimps, crabs and such. These are all beautiful creatures that do not require light. I wouldn't waste my money on corals though...more than likely they will just die in a few weeks or months.