Difference between freshwater and saltwater flake foods

[Bruce7267ad]

So I was going through some of the saltwater and freshwater flake foods at my local aquarium store and noticed that they're quite a bit of similarities between the two especially in a brand called Omega one which I know Petco and PetSmart sell.
Does it really have to be saltwater flake food to give to a saltwater fish
Or can I use freshwater food?

 

[Charles Washington]

It's all up to you but to be on the safe side use what your fish is????