The earliest black goldfish to appear is the ink dragon eye, the tail fin is developed, and it is famous in ancient times. As early as 1592 AD, the nascent goldfish was bluish gray, and after two months it gradually turned from blue-gray to iron-colored, and if it could then turn into a black like a squid, it became an ink-colored fish. The progress of each fish fading varies, and if it can remain unchanged, it is a treasure if it grows to the point where it is still thick and black as ink
