It can but a more likely situation would be that the frog doesn't notice it and the fly just pollutes the water. Frozen-not freeze dried, bloodworms are a good choice. Live bloodworms, blackworms, earthworms or nightcrawlers(cut up), and frog pellets are good choices. The earthworms are very nutritious as well (remembering they must be cut up for the frog). Variety is also important in the frogs diet.