Why do all salt water fish taste different but eat pretty much the same things?

This is not necessarily true. While many saltwater fish species do share similar diets, they can vary in taste due to several factors:

Diet: Even though saltwater fish may eat similar types of food, such as plankton, small crustaceans, and other aquatic organisms, their specific diets can vary depending on their species, size, and habitat. Some fish may have a more varied diet that includes a wider range of food sources, while others may specialize in consuming certain types of prey. These differences in diet can contribute to variations in the flavor and texture of the fish.

Habitat and environment: The environment in which saltwater fish live can also affect their taste. Factors such as water temperature, salinity, and the presence of certain minerals and nutrients can influence the fish's metabolism, growth, and overall flavor profile. For example, fish living in warmer waters may have a higher fat content, resulting in a richer flavor, while those from colder waters may have a milder taste.

Cooking methods: The way saltwater fish are cooked can significantly impact their taste. Different cooking methods, such as grilling, baking, frying, or steaming, can enhance or alter the natural flavors of the fish. The use of herbs, spices, and sauces can further add layers of flavor and taste.

Individual variations: Just like humans, individual fish within the same species can have slight variations in taste due to genetic differences and other factors that influence their growth and development. These individual variations can contribute to the unique flavor profiles observed among saltwater fish.

Therefore, while saltwater fish may share some similarities in their diets, variations in diet, habitat, cooking methods, and individual differences can all contribute to the diverse range of flavors and tastes experienced when consuming different species of saltwater fish.