last night was an exception though, i lost my 3" common bristlenose , he must have been dead for 2 days max( thought he was hiding in his cave), when i pulled him out the smell was enough to almost make me sick so toilet he went ..
I said other because my LFS lets you give back the fish if it dies within 3 days, but if it is longer than that (since I can't vote twice) either flush it, trash it, or use it as compost like the fish you eat when you throw it away.
I usually put it in one of those tiny little plastic bags so it doesn't smell, then put it in the garbage.
I often do that too, cos I like to look closely at it through the bag (I don't like directly touching the dead body) if I'm not sure what it died from, e.g. if I'm looking for parasites.