Is Bleach episode 304 filler?
Filler Yes, episode 304 of Bleach is filler.
#304
Another Side Story! This Time's Enemy Is a Monster!?
外伝再び!今度の敵はモンスター!?
Aired 11 Jan 2011
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.