Is Bleach episode 151 filler?
Canon No, episode 151 of Bleach is canon.
#151
The Raging Storm! Encounter with the Dancing Arrancar
吹き荒れる暴風！踊るアランカルとの遭遇
Aired 5 Dec 2007
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.