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.