If all of the Neptunian moons could be combined into a single object, Triton would account for over 99% of the mass.
Triton is the only large moon in our solar system with a retrograde orbit (meaning it orbits in the opposite direction of Neptune’s rotation). For this reason, Triton is believed to be a former Kuiper Belt dwarf planet that was captured by Neptune’s gravity.
Speaking of the Kuiper Belt: it was named for the same astronomer who in 1949 discovered one of Neptune's small moons, Nereid, by looking at photographs taken through a telescope. Although the moon Proteus is significantly larger than Nereid, it was not discovered for another 20 years (not until the 1989 Voyager flyby). This is because it orbits so close to Neptune that, when viewed through telescopes from Earth, Proteus is lost in the glare of sunlight reflecting from its host planet.
On the other hand, two of Neptune's moons have more distant orbits than any known moons. One of them, Neso, is sometimes at a greater distance from Neptune than Mercury's distance from the Sun! At the scale of this Solar System model, Neso would be a microscopic particle orbiting Neptune at an average distance of about 33 feet (or 11 paces).
You can view these links to learn more about Triton and the other moons of Neptune:
