If you mean acclimating starfish, beneficial nudibranchs, urchins, chitons, cowries and abalones, which are constant feeders, count them as an invert. If it arrives with identical salinity, good: give it a rinse in salt water to clear away or at least thin out any bag water clinging to it and it's good to go. If not, you can take them over in a matter of an hour or so. Set up your qt tank as the waystation: you don't have to fill it all the way, and in the case of some of these under-rock creatures that have incredibly strong attachment to rock or glass, I'd do this in a container other than glass, like a plastic liner in a bowl, because you can hurt them trying to get them unstuck: a surface that will bend is much easier, though I've seen some stuck so well that the answer is to drop the whole bowl into the tank and retrieve it later. Gradually bring the salinity to match your tank, and it's good to go, after a little while, say 30 minutes, at the matching salinity. This gives the last adjustment time to work all the way through its tissues before you change its environment yet again and drop it into a place where fish may be curious about it. Just a hint on inverts: if you have fish like wrasses or dottybacks, which tend to bedevil anything new, tank-twilight is a good time to go ahead and put a new critter in, which lets it get rightside up and wander off to a place of safety without hassle. This is particularly true with the shellfish, which generally prefer the dark: you only see some of these out and about by flashlight examination of your tank.
[One caution on starfish in general, just as a type: most classic-shaped stars are not at all reef friendly, and those that are reef-friendly (the linckias) should not be in a tank younger than a year or so, or owned by anybody who has not had a couple of years' experience, because their feeding habits are not well understood and they are quite fragile. They seem to eat film on rocks, and are otherwise expert-only.]
