Pupfish

The Pupfish is a critter that spawns infrequently in bodies of water in the Desert biome. Like Goldfish, they swim passively back and forth in water. They can be caught with any Bug Net to be carried around in the inventory and released later, or crafted into a Pupfish Bowl to be used as furniture. Once crafted, the bowled Pupfish cannot be released again, and when placed down it moves around inside the bowl as it would do outside.

Unlike many critters, Pupfish are capable of spawning on-screen.

Trivia

 * Much like the Terraria critters, real-life are usually only found in intense conditions and isolated locations, such as the rare  which is only found in its namesake, a water-filled cave in.
 * Unlike the Gold Fish Bowl, the Pupfish Bowl is not an armor or accessory item, nor is the Pupfish a consumable food ingredient.