What is the difference between 'freshwater' and 'saltwater' fish?

What is the difference between 'freshwater' and 'saltwater' fish?

Marc Grover (Professional Aquarist) gives expert video advice on: Are goldfish easy to take care of?; How many fish should I get to start an aquarium?; How do I choose a healthy fish? and more...

The difference is right in their name. Freshwater fish come from fresh water, whether it's lakes or rivers. Saltwater fish come from the ocean. A lot of freshwater fish are bred in captivity, whereas a lot of saltwater fish - almost all saltwater fish - are not, they're actually wild caught. The differences in equipment can be pretty dramatic. The differences in longevity and durability can also be pretty dramatic. Freshwater, because a lot of them have grown up their entire life in captivity, they don't have a lot of adaptation. Whereas saltwater fish have a tremendous amount of adaptation. So your equipment has to be top of the line and your patience has to be top of the line with them as well. Typically, I tell people expect more fish losses. If you did everything perfect and everything were equal, in a salt water-type system than fresh water just because of the nature of the fish itself before you get it.