In the growing season, the plants should be watered at least once a week. When watering, the soil should be given a good soaking, allowing excess water to drain away. Allow the compost to dry out slightly between each watering.
Cacti fertilizer requirements are pretty simple. Any good houseplant food (diluted to half) that's higher in phosphorus than nitrogen is a good choice. A 5-10-5 solution can work well. Now that you know that they really do need fertilizer, it's also important to know when to feed cactus plants.
Although slow-growing, a cactus plant is fairly self-sustaining as it stores moisture in its roots, leaves and stems, and so largely regulates its own food intake. A cactus plant likes a light, airy and warm spot – but not too hot, around 18°C is ideal – and can cope well in direct sunlight.
Some cacti species are well adapted to do well in full sunlight and will tolerate extreme heat conditions whereas others will need full protection from intense heat. However, a majority of cacti species need warm weather to survive. Therefore, the ideal temperature for most of them is anything between 45oF and 85oF.
Shake off the old soil and plant the cactus at the same depth it was growing in the old soil. Fill in around the roots with your medium and place it in a sunny southeast or east window. Among important repotting cactus tips is to not water the plant yet, as it is adjusting to being handled and new soil conditions.