Why's the octopus awake? Night at the Seattle Aquarium

It’s almost midnight, and Bailey is still awake, stretching and pushing against the glass in front of her.

Bailey is an octopus at the Seattle Aquarium, and she’s not the only one awake. Michelle Arnett is the night biologist at the Seattle Aquarium, and she's making her rounds.

Arnett works in semi-darkness, occasionally flipping on a flashlight with a red, muted glow because, despite the wakefulness of some residents, it’s nighttime for the animals, too.

It’s the octopuses you want to keep an eye on, she said. The top of the exhibit has a ring with Astroturf on it, something the suckers can’t stick to, so they can't climb out.

Many of the tanks are inky black behind the glass.

[Read the rest of the Night Shift series.]

Ghostly shapes and silver flashes serve as a reminder that they’re filled with life. Simulated moonlight shines into some of them, illuminating the outlines of rocks, coral and large fish with crescent-shaped tales. It saps the tank's interior of the vivid colors visitors might see in the day.

Arnett spends most of her time monitoring the many filters that keep water flowing and the animals alive. She listens as she walks around.

If something sounds weird, it usually means something is wrong.

“A lot of people don’t know the mechanics that go behind an aquarium,” Arnett said. “Even the little tanks need so much equipment monitored at all times.”

As we walk through the dark, she pauses. "Do you hear that?" she said. "It's just a tiny little roar.”

We listen, looking into the dark water in an enclosure.

"There he goes. And he sees us. What are you doing awake?" she says, addressing the harbor seal swimming in the dark. "You're not normally awake right now."

Two of the harbor seals, Q and Hogan, are awake. Their growls sound like a truck rumbling in the distance.

Barney is the third harbor seal in the enclosure, and he's asleep. He’s 33 years old, ancient for his kind, according to Arnett. He’s always napping, she said. Nearby, the fur seals might be up, too.

"They must both be back there, because I don't see them,” Arnett said.

Or maybe they've broken out, I offer?

“That is one of my duties at night, to make sure that doesn't happen," Arnett said. She's new-ish, so she's never dealt with a jail break — but she's heard stories of close calls.

At this hour, Arnett and the night security guard, Liam Paige, are the only people around.

Paige said he likes working nights at the Aquarium because the fish never complain. His favorite is the puffer fish.

Arnett said the puffer fish is everyone’s favorite at night. She’s about the size of an adult human’s head, and she’ll follow the staff from window to window as they do their rounds, bobbing in front of them when they stop.

It's just before 1:30 a.m., and Arnett still has hours ahead of her — checking seawater filters, freshwater filters, pumps, water levels and temperatures. She’ll be off to bed by the time people start to pour back into the site in the morning.