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the "green" jellyfish are moon jellyfish (Aurelia aurita)
and the purple/pink jellyfish looks like a black sea nettle (Chrysaora achlyos) but it is difficult to tell with the lighting.
What aquarium were these photos taken at? They're great!
does belong in the jellyfish category (cnidaria), class hydrozoa
definately looks more like a Chrysaora quinquecirrha (east coast sea nettle) to me. check again next time you visit your aquarium. sometimes there is a delay or miscommunication between the husbandry staff, the graphic dept. and the gallery guides.
one of my favorite fish to watch. so pretty & fiesty.