A tropical fish cannot be cooked but is still edible. It restores half a bar of hunger which makes it impractical compared to other foods. However, tropical fish can be helpful if a player has a whole stack of them, or if they are the only available food source in an emergency situation.
The tropical fish, like any other fish, can be found while fishing in any body of water. To help increase the odds of obtaining this fish, fishing rod enchantments (Lure and Luck of the Sea) can be added to a fishing rod. With an unenchanted fishing rod, the chance of catching a tropical fish instead of a normal fish is approximately 2.0%. As of 1.13.1, players can kill tropical fish mobs to get it, though this is a less efficient way of obtaining it than fishing.