I did salt for some 20 years before going freshwater planted. I really disagree with those who say it's too fussy for a nano. It is, in fact, quite easy and lovely. I even had a 7 gallon biOrb set up as saltwater [with it's funky undergravel filter!] and bred a pair of clowns in it.
Get a copy of the book The New Marine Aquarium by Paletta--it actually walks you through a tiny set-up. You do need to be careful with stocking--and don't bother with anemones or coral. A really nice set up can be put together with a 6 gal nano cube, no sweat.