Definitely not polyps. Explain to him that they can sting corals and fish and will easily over run a tank (As you're seeing right now). Causing problems in the long run. Also, you can introduce a file fish to the tank, or certain rabbit fish, or give peppermint shrimp a try. A file fish will have the tank cleaned out of it in no time, but, then you have to figure out what to try and feed it after it's all gone. Best of luck, kill it all!!