Light is one of the basic requirements for plants.Adequate sunlight is necessary for cactus plants. Keep indoor cacti on windowsills or other places, where they get sufficient sunlight.The amount for light needed differs in different cactus. Most cactus need a dry environment. They can tolerate temperatures between 45 to 80º F.The pots in which they are planted should have a good drainage, as water retention can cause rotting of roots.Clay pots are the best option for cactus plants. The pot should be three to four times the size of the plant. Fill the pot with the planting medium, which should be dry.Refrain from watering the cactus for a week after planting. During this time, the plant will get adjusted to the new soil or planting medium. After that, water the plant once in every week. During winters, watering should be restricted to once a month.