Dunno... Incorrect temperature kills a lot of captive corals, even at small variations. Is a diverse group and some are harder to kill than other. On the other hand, Cnidarians taste their food and reject often small stones and sand grains. Probably many types of plastic particles (if not all) would be just taken by a small peeble and ignorated. Cnidarians loose interest quickly when you touch its tentacles with an inert matherial.