Jellyfish are among the original drifters — going with the flow for millions of years, since before the dinosaurs.

Moon jellies are one of the more than 300 species in Puget Sound. They’re translucent and only mildly toxic, unlike their lethal cousins from Australian waters that can kill a human.

But for such simple, mainly made-of-water creatures, jellyfish require a complex environment if brought indoors to live in an aquarium.

To stay healthy, the 150 jellyfish in the circular tank at Seattle Aquarium need to have their home cleaned quarterly. It is staff biologist and diver Kathryn Kegel’s task to scrub the interior surfaces in the 12-foot doughnut.

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Another staffer first uses a small dip net to carefully remove the moon jellies and hold them in buckets.

It takes longer for Kegel to gear up than to clean the aquarium. With sensitive skin — the jellyfish cause her to break out in a rash — she completely covers up because thousands of the creatures’ microscopic stinging nematocysts are left in the water.

Kegel slips in from a hatch on top.

The water continues to circulate, at a pace of about five minutes per revolution.

At first she found the kreisel, or circular tank, “very claustrophobic” though it’s completely clear. It’s only 41 inches wide inside.

But after a few times, “it wasn’t intimidating. I’ve got a job to do.”

She says she focuses on the task at hand not the room beyond. The two lights that alternate colors — red, green, white, purple, blue — continue to illuminate as she cleans.

She appreciates the uniqueness of it. Like the jellyfish, Kegel goes with the flow.

Alan Berner: 206-464-8133 or aberner@seattletimes.com