My first SW tank would be considered a nano and was back in 1971 when I saw an ad in some magazine for a pair of mated dwarf seahorses for $3.
On recommedation of a neighborhood LFS a woman ran out of her renovated garage, my mother bought me a 10g aquarium with an incandescent hood, some salt (IO if I remember right), a floating hydrometer, air pump, corner box filter and a couple of plastic plants (for hitching posts).
Of course, since I knew absolutely nothing about SW aquariums and info was even harder to find for an 11 year old kid in those dark, pre internet days... the tank only lasted about 6 months. It was over 10 years later before I got back into the hobby with FW tanks again, then SW about 3 years ago.