[i have crabs]

the best route really depends on alot of things, if he is the only fish in the tank, do you have another tank you can qt and medicate him in.
if he is not the only fish and i would guess thats the case removing him and treating him in a qt will probably work but soon as you add him back to the "infected" tank he will be at risk of another outbreak. in a situation with many fish it might be better to just start adding garlic to his food maybe get a cleaner shrimp and hope he can fight it off and keep it under control,this method will leave "ick" in your tank but the fish will usually be able to keep it from becoming a problem, personally i hate this route unless it has to be done.
if you want to get rid of the ick and actually cure the fish of an annoying parasite all the fish in the tank need to be removed and treated, i recommend seachem culprimine its always worked great for me and ive never had an issue, thier are other medications and treatments but i think this is the easiest,cheepest and least stressfull. the tank will have to be fishless for a good 6 weeks and it probably wouldnt hurt to add a reefsafe ick cure just to help guarantee the tank is good before re adding the fish.
thier are many ways to handle this so i hope i can help