How big can a hexagonal dinosaur fish grow? 20 to 30cm. According to the relevant public information, the scientific name of Hexagonal Dinosaur Fish is Mexican Blunt-mouthed Salamander, also known as American Salamander. It is an amphibian of the genus Blunt-mouthed Salamander, which belongs to the family Blunt-mouthed Salamander. Hexagonal Dinosaur Fish can grow to 20 to 30cm, grow well and grow to more than 40cm. If you want to make Hexagonal Dinosaur Fish grow bigger, you should pay attention to providing them with sufficient food and a stable living environment.