What is the world's smallest type of fish?

The world's smallest fish is Paedocypris, a genus of cyprinid fish that is found in the forest streams of Southeast Asia. Paedocypris fish are small enough to fit on the tip of your finger, and their average adult size is only about 7.9 mm (0.3 inches) in length. They are so small that they have to eat tiny organisms like plankton and insect larvae.

Paedocypris fish have unique adaptations to their small size, such as an abbreviated lifespan, a compressed body shape, and reduced bone tissue. These adaptations allow them to survive and thrive in their low-oxygen and acidic environments. Despite their size, they have a complex skeleton and nervous system, which makes them interesting subjects for scientific study.

Paedocypris fish were first discovered in 2006, and there are currently two known species: Paedocypris fisheri and Paedocypris micromegethes. These tiny fish are not commonly kept in aquariums due to their specialized habitat requirements and fragile nature, but they have become popular among fish collectors due to their novelty and unique characteristics.

The world's smallest fish is the Paedocypris progenetica, a type of minnow that is native to the peat swamps of Southeast Asia. Adults of this species typically reach a length of 7.9 millimeters (0.31 inches), making them the smallest known vertebrate. Paedocypris progenetica are found in acidic, oxygen-poor waters, and their small size is an adaptation to these harsh conditions.

Here are some other small fish species:

• Schindleria brevipinguis, a type of goby that is native to the Great Barrier Reef. Adults of this species typically reach a length of 7.0-8.4 millimeters (0.28-0.33 inches).
• Pandaka pygmaea, a type of goby that is native to the Philippines. Adults of this species typically reach a length of 7.5 millimeters (0.30 inches).
• Trimmatom nanus, a type of goby that is native to the Indian Ocean. Adults of this species typically reach a length of 7.5 millimeters (0.30 inches).
• Photocorynus spiniceps, a type of anglerfish that is native to the deep sea. Males of this species typically reach a length of 6.2 millimeters (0.24 inches), while females can reach a length of up to 50 millimeters (2.0 inches).

It is important to note that the smallest fish in the world is a matter of debate, as there are many small fish species that have not been fully studied. It is possible that there are even smaller fish out there that have yet to be discovered.