Chemical warfare is more of an issue with soft corals, and frogspawn is actually a stoney coral. You certainly don't want them touching, since both have stinging tentacles, but as long as they're not doing that, they should be fine. Keep in mind that Euphilia genus corals like frogspawn do have long sweepers tentacles that can sting other corals, and I suppose anemones (though I'm not sure a frogspawn would win a fight with an anemone). I've never had a frogspawn, and I've never seen these sweeper tentacles on my hammer, so unfortunately, I don't know much else about them.