Found these in my tank should I be concerned?

[Efaro85]

Noticed these tonight, just recently had a Dog Faced Puffer, Lionfish, and Koran Angel die days apart. My Hawkfish, Snowflake Morray, Condy Anemone, Starfish, Hermit Crab, and all snails are are good, and Corraline Algae growing well. 120 Gallon tank well established. Any help would be greatly appreciated.

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[Sugar Magnolia]

Hydroid jellies, they'll disappear on their own.

 

[Efaro85]

Thank you for the heads up.

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