Sardinium

"When I get my hands on these fish I might exchange them on the range, Except that they look so delish..."

- Agent 8 on the Sardinium mem cake

Sardinium is an item in Octo Canyon used to upgrade weapons at the Ammo Knights Enhancifier.

One Sardinium can be found in each Octo Canyon mission. Standard missions have a hidden Sardinium that the player must find, while each boss mission's Sardinium appears in front of the Zapfish after the boss is defeated. There is also one hidden Sardinium in each sector of Octo Canyon.

A Sardinium that has already been obtained once before will appear in the same location but with a muted appearance, and picking it up gives the player five Power Eggs instead.

In Return of the Mammalians, Sardinium reappears and is used to upgrade the Hero Suit and gain new abilities. They can be obtained by clearing certain patches of Fuzzy Ooze with Smallfry, breaking open Crates and Loot Anchors in Alterna, and defeating each member of Deep Cut. Unlike in, Sardinium is no longer found hidden within missions.

Trivia

 * Sardinium pieces resemble niboshi, dried sardines used in cooking, but with a metallic texture and an eye resembling the head of a Phillips screw, hence the name combining "sardine" and "-ium", a suffix used for metals.
 * Despite their metallic appearance, Agent 8's poem on the Sardinium mem cake suggests that they may be edible.
 * The Art of Splatoon 2 mentions that Sardinium is used as the material attaching the Ink Tank to its harness and that the heels of the Neo Octoling Boots are also made of Sardinium, describing them as "hard and heavy."