Is ONE PIECE episode 550 filler?
Canon No, episode 550 of ONE PIECE is canon.
#550
Something Has Happened to Hordy! The True Power of the Evil Drug!
ホーディの異変！凶薬の真の力
Aired 3 Jun 2012
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.