Moon cactus plants are known as Gymnocalycium mihanovichii or Hibotan cactus
Gymnocalycium mihanovichii v. rubrumGymnocalycium mihanovichii v friedrichii (green flower)
Light: The moon cactus plant requires bright indirect sunlight. Full sun will actually harm this container plant, so keep it out of direct sunlight for long periods of time.
Water: Water moon cactus thoroughly, then let the plant dry out between waterings.
Fertilizer: You don't need to regularly fertilize your moon cactus plant, but you should dose it with a cactus fertilizer every month during its growing season (April to September).
Temperature: The tiny moon cactus won't do well in very cold temperatures, so bring it inside to overwinter during the cold winter months.