Glass catfish

Well, the glass catfish also known as the ghost catfish has many muscles that are completely invisible, which makes them perfect for camouflage. Even though their skin is completely transparent, you can actually see their internal organs and even their spinal cord. These beautiful transparent creatures can be found in the Southeast Asian waters and they are also well known for their swimming skills. 

If you want to own an exotic pet, you can have a glass catfish as a pet but you should be aware that they require a medium level od care. They are really shy, so you should choose their aquarium mates based on similar personality traits. These species are very peaceful by nature and compatible with silver dollars, tetras, dwarf cichlids and danios.