This ID is for the Nudibranch at the bottom center of the photo: Dondice parguerensis - A March, 2022 paper, "Integrative systematics of the genus Dondice Marcus, 1958 (Gastropoda, Nudibranchia, Myrrhinidae) in the Western Atlantic, Kimberly García-Méndez & Vinicius Padula & Ángel Valdés" has reclassified this as Dondice parguerensis, sp. nov.
Lifer!
On floating seaweed/bryozoa, placed in aquarium