Cacti and succulents do better with very little, infrequent fertilizer. If you feel like you have to feed them, use quarter strength complete fertilizer only once or twice a year. I use leftover orchid food, diluted way down. Outdoor plants in the ground are never fertilized and do just fine.
Most indoor succulents never get enough light or heat. Add fertilizer, and their growth gets weak, soft and leggy. Generally speaking, a grow light will help your plants a lot more than fertilizer will.
