is one piece episode 169 filler?

Aboard the Going Merry, Gan Fall begins to explain Sky Warfare to Sanji, Nami and Usopp. He demonstrated this by having Sanji hit the Impact dial with a large hammer, to no avail.

Gan Fall tells Sanji to press the tip of the dial, causing a blast to be emitted from the shell. Gan Fall further explained how some other dials are used for warfare.

When asked about Mantra, Gan Fall told them it is difficult to explain, however he was able to explain some of the basics, and told them what the hearing capabilities of the priests and Enel were.