Complex sentence: Flounder, Ariel's best friend, is a bright yellow and golden blue colored tropical fish called a juvenile blue tang (dispite the name, he is not a flounder), but is more similar in appearance to a convict tang or a clownfish.
Split into simpler sentences: Flounder, Ariel's best friend, is a bright yellow and golden blue colored tropical fish. Despite the name, he is a juvenile blue tang not a flounder, but is more similar in appearance to a convict tang or a clownfish.