Stopped at the Border

[Delphinus]

My understanding is that zoanthids are not listed under CITES. (Note it's CITES not CITIES, everyone spells it as CITIES and that's incorrect - "Convention for the International Traffic of Endangered Species"). If you go to cites.org, there is a species lookup that will look up Appendices 1 and 2 and possibly 3 and if it doesn't show up there, then it's not listed on CITES and you don't need CITES documentation.

That said, now the onus is you and the shipper to prove emphatically what species is contained in this shipment and that it's not covered under CITES and I'm not sure what you can do to prove to customs that this is the case. At a minimum starting point you're going to have to get in touch with your supplier and ask them for help on this I think.

Good luck.