Goldfish

Goldfish are benign background characters that cannot harm the player, similar to Bunnies. They have only 5 health (which means that they will almost always be killed with a sword first time) and can be damaged by other mobs.

During a Blood Moon, or when hit with Vile Powder, Goldfish turn into Corrupt Goldfish, which have more health and do attack players. These do not drop the Goldfish item.

Tips

 * The Fish Statue can be used to farm the Goldfish drop. Dart Traps or Lava can be used to kill the Goldfish as they spawn. (This does not apply to the PC version of the game due to version 1.2.3. They still drop the banners upon being killed, but to catch the goldfish item, use the Bug Net.)
 * Another farming method is to find a water body where Goldfish spawn, and corrupt one of them with Vile Powder. Further spawned Goldfish will be killed by the corrupt one, leaving behind the Goldfish item. The Corrupt Goldfish will likely despawn when off-screen for too long, and new Goldfish will not spawn while the entire water body is on-screen; keeping an area of the water off-screen may allow new fish to spawn while keeping the Corrupt one around. (This does not apply to the PC version of the game due to version 1.2.3. They still drop the banners.)

History
Poisson Goldfish (NPC) Goldfish (NPC) Золотая рыбка