* Definition of "tropical fish": The term is broad. It can encompass fish found in tropical saltwater (coral reefs, etc.) and tropical freshwater habitats (rivers, lakes, etc.).
* Constant discovery: Scientists are still discovering new species of fish, particularly in unexplored areas like the deep sea.
* Taxonomic changes: Scientific classification of fish is constantly evolving, with new species being identified and existing ones being reclassified.
However, we can give you some estimations:
* Saltwater: Estimates suggest there are over 2,000 species of fish found in tropical coral reefs alone.
* Freshwater: The number of freshwater tropical fish species is much higher, with estimations reaching 10,000 or more.
Therefore, the total number of tropical fish species could be anywhere between 12,000 and 20,000 or more.
Keep in mind that this is just a rough estimate, and the actual number is likely to be much higher.