Complex sentence: As jellyfish are not even vertebrates, let alone true fish, the usual word "jellyfish" is considered by some to be a misnomer, and American public aquariums have attempted to popularize use of the terms "jellies" or "sea jellies" instead.
Split into simpler sentences: As jellyfish are not vertebrates, let alone true fish, the word "jellyfish" is considered by some to be a misnomer. Public aquariums may use the terms "jellies" or "sea jellies" instead.