For somebody who is interested in starting with Aquatic mosses, Riccia Fluitafns is a highly recommended moss. It's hands down the easiest and most forgivable moss that will honestly explode with growth in almost as conditions!
 
Size Per order: Portion Cup
Lighting: Low
Substrate: Not needed (Don't plant in the substrate)
Temperature: 60-83
Difficulty on a scale of 1-10: 2
Color: Bright green
Species of plant: Riccia Fluitans