bc564, i have two words for you my friend: tide pools. The species that get stuck in tide pools have to be able to adapt to large and relatively quick changes in salinity and temperature. I would run a couple of fans on that tank just in case and not let the tank drop below 8deg if i could help it.
the nice thing about tide pool tanks is that specimens are not hard to find. the beach is your lfs.
as you might be able to tell, Ive been thinking about this too. My fave local (cold of course) species, although it isn't tidal, is the pacific spiny lumpsucker. They look ridiculous.
