Cactus plants do well indoors with minimal care, as they only need light, food and water to thrive. Light is the most important, with food being second. Water can allow a cactus to grow or, if it's overwatered, cause it to die. To grow cacti indoors, you will need growing containers with good drainage to keep the roots of the cactus from contracting root rot. Cacti should be repotted as soon as possible after purchase.
Fill the growing container with a layer of pebbles or marbles at least 1/8 the size of the pot. For a 6- or 8-inch pot, an inch of pebbles will work fine.
Fill the remainder of the pot with the cactus potting soil.
Remove the cactus from the old growing container, shaking off any soil that stays on the roots.
Dig a hole in the growing medium just large enough to place the roots of the cactus in without crowding.
Place the cactus root in the hole and spread out the roots. Cover with additional soil, pressing down firmly around the root to remove air pockets.
Place the cacti in a windowsill where it will receive light but not direct sun. Direct sun can "burn" a cactus plant.
Water as the soil dries out. This could be as little as once a month. Test for dryness at least once a week by inserting a pencil or wooden down in the soil. If the pencil is dry when removed, it is time to water.
Feed the cactus a 5-10-5 fertilizer according to label instructions three times a year during the spring, summer and fall. Do not feed it during the winter months.