If you watch water quality closely, I imagine you will be fine.
Offhand, have you ever tried spot feeding it? Something like a small bit of shrimp on a bamboo skewer, touched to the arms to see if it will take it? Few do, but it is worth trying.
If you want to "put it down" I can give you tips. The best way for seastars is a reverse acclimation (put it in a bucket with a bit of saltwater and slowly add seawater). This effectively "relaxes" it.
Whenever I mention this I feel I must bring up Steinbeck, who actually refers to this in "sweet Thursday"
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Doc got back from his collecting about four-thirty... and submerged in sea water in his collecting buckets were hundreds of brittlestars. He moved the brittlestars to a large, flat-bottomed glass dish and poured some sea water on top of them. The little animals with the snakelike arms whipped about for a moment and then settled down. When they were quite still and resting Doc added a little fresh water to the dish. The arms stirred nervously. He waited a while and then added a little more fresh water. To a sea animal, fresh water is a poison, and if it is slowly introduced it is as subtle as morphine. It relaxes and soothes until the little creature goes to sleep and dies without violence."
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Oddly enough, to me this is one of the more beautiful passages I've encountered, specifically the last sentence, perhaps due to the compassion shown to "little creatures."
A similar effect can be achieved with Epsom salts. Put the star in a shallow dish with seawater and in a corner put a tablespoon or so of epsom salt. Every so often, tip the tray to dissolve some salt. It, too, is an effective "relaxant" and over time the star will stop moving.