I`m a little confused, are there different kinds of "Ich"? Is there a kind
that is not contagious?

When I introduced a super-juvie Hippo Tang 4 months ago, it broke out in
white spots for a few days, but it went away on its own after soaking its
food in garlic for a few days. Ive never seen my other fish have any
symptoms (knock on wood).

Ive read many similiar posts in reef forums. There seems to be a lot of
people who have Tangs break out in "Ich"--- but then do water changes or use
the lights less and their Tangs also recover W/O any dipping or medication.