I'm in the same dilemma with my outdoor mini/table top garden.
The thread "Well it's a start..." in
Miniature Gardening forum
I was told to mix Elmers Exterior Glue with builders sand. Builders sand doesn't shift like other sands do. Use this mixture as a base for your blue sand or blue glass pebbles. I still think at least in my case I'm going to need a "river bank" or something similar to keep the soil on the sides from spilling into the river.
