Actually they feed best after dark, in the dark they are "deadly" lol. I always fed mine at night, they would skim pellets off the surface much better at night. I always thought the surface feeding if for insects at night. A school of tiny fish will be rounded up at night as well.
In the wild gambusia consume a large number of other small fish to the point of being a threat to gamefish young. The guppies, while capable of eating their own young or other fishes young they are smaller as adults and nowhere near as aggressive.
