Arcane Archer Enhance Arrows

[BDD]

A discussion came up Concerning the Arcane Archer Prestige class. Does the Enhance Arrows (SU) cost 1 standard action. My thoughts are it does but another disagrees. Reading the wordage on Supernatural Abilities, it does unless the descriptor states otherwise. The paragraph makes no mention of actions
Both Paladins and Monks have SU that specifically state other actions are used.

Tks
B

[SteelDraco]

There's no action involved - it automatically applies to every arrow he shoots from when he gains the ability for the rest of his adventuring career.