Defiantely NO. FW fish are very fatty fish, and SW are "fit" fish. Idk about the side effects yet, but i know it is not a good thing. It would be better if you just used BBS which is better anyway, or a frozen food such as mysis.
quaddity- i dont think guppies can live in SW. otherwise everyone would have guppies in their SW tanks. Guppies can however live in a slightly salty water, but this is only in the home tank used for treating parasites.