Gambusia are predatory on anything living that is small enough to fit into their mouth. I think they eat more newly hatched fish fry than fish eggs. Fish fry quickly grow beyond edible size for Gambusia, but for a short period Gambusia eat lots of littoral fry. The most susceptable fry are non- sunfish/bass fry. Sunfish/bass fry have parental guarding and once they leave the nest, they are probably too large for Gambusia to injest. Most vulnerable fry would be minnow fry and other fish that are not nest builders.
Deb, put some newly hatched fathead fry in an aquarium with adult Gambusia and you can verify my comments.
