Do great white sharks eat lionfish?

Maybe, if given an opportunity Yes. But, Lion fish is not one of the Great Whites regular prey species. Great Whites prey upon fish (like Tuna, Rays etc), other smaller species of Sharks, dolphins, porpoises, seals, sea lions, sea turtles, sea otters and even sea birds. They prefer prey that has a high content of energy rich fat. They usually hunt early in the morning before the sun rises fully, when the visibility is poor