The White Margined Unicornfish (Naso annulatus) is an unusual looking fish species that belongs to the ‘Surgeonfishes’ family Acanthuridae which also includes ‘Unicornfishes’ and ‘Tangs’. This species can be found living in the warm tropical waters of the Indo-Pacific where it can generally be seen in large schools along coral reefs generally in depths greater than 25 metres. The body is silver-blue in colour whilst the horn on the front of the head does not develop until the fish is approximately 20cm in size. Original public domain image from Flickr