Is ONE PIECE episode 228 filler?
Canon No, episode 228 of ONE PIECE is canon.
#228
Duel Between Rubber and Ice! Luffy vs. Aokiji!
ゴムと氷の一騎打ち！ルフィＶＳ青キジ
Aired 27 Mar 2005
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.