You need to go you YOUR vet if you have other animals that you take. The reason is they will be much more likely to listen to you and to help you because you are already a customer of theirs. If your reef is your only pet it can get hard because they would rather not mess with it because them writing you a script or even selling you the meds is not very profitable for them.
Wherever you end up, take in a copy of dustins treatment plan and also you could take pic to show the vet and explain that its similar to your dog having fleas. they are a parasite and they host on the coral, make sure you let them know that they are damaging your animals health.