[It is normal behavior for clownfish to nibble/suck the tentacles of anemones or other corals they host. Sometimes they can bite/rip off tentacles, but it is not a feeding issue.]
[As Amanda hinted he's sing it as his anemone! Do watch it closely as they can kill things with their behavior sometimes. If it starts to look bad try moving the frogspawn somewhere else. If it continues you'll have to choose one or the other ]
]