The meds that Navarre mentioned are classed as 'Reef-Safe' so you should be ok with the starfish.
If you are in an emergency situation then I would recommend the freshwater bath technique. This will cause the parasites to explode due to Osmosis but has no real ill-effects on the fish. The major thing to be careful of is the time that the fish is in the bath and always keep watching the fish. It is normal for the fish to lie on the bottom and gulp but use your own judgement on its health. Do Not exceed 6 minutes in a freshwater bath and never, ever bathe a Dragonet as you will kill it.
I would also try and get some Garlic Extreme (Garlic Extract) and dip the fish food in this before feeding. The garlic essence is very strong and this permeates through the fishes scales once digested. The effect this has is to make the fish very smelly to the parasites and will discourage them from hosting on the fish. This is ideal if you've just given a fish a freshwater bath as you don't want to kill the parasites only to re-introduce the fish back into an environment where it has a high risk of re-infection. Ideally a QT tank would be good as you could dose the fish with copper meds which usually work a lot better than reef-safe ones
In the long term, a UV steriliser will help control parasites and, even better, ozone as nearly every fish tank has the Ich parasite living in it, whether its dormant or active. Prevention is better than cure!
