Try this type of pot filler called garden genius :
http://www.3m.com/brands/garde... I found them at a Walmart store.
The material and texture reminds me of kitchen sponges, so I think you can also use those nylon kitchen sponges found at dollar stores. Then just put a weed fabric on top of it before you add in the soil.
For my succulents in containers, I maintain shallow depth, since I grow most of them outdoors year round, so I prefer to keep the depth like that of a bonsai container, around 3 to 4 inches especially if the plants are still very young. I do use bigger clay pots too and I use fillers like styro peanuts or inverted plastic containers and then weed fabric, then the soil. It is too windy here at times, so containers have to be sturdy and heavy. But just the same the soil is at a depth of 4 inches.
