WinterWind said:Either two ADF's or a single male betta. I'm not sure guppies or tetras would do very well it a 1.5 gallon tank. ADF's are small and don't need very large spaces, so a 1.5 gallon is ideal. And a betta would be quite happy in a 1.5 gallon compared to a cup or small bowl.
When I was around 11 years old I kept guppies in a gallon-sized mayonnaise jar changed over to fish-keeping. They thrived and bred, and it was running for well over a year.