i use a plant or two with good air flow. the containers your using are fine if you put holes everywhere. if you can get a good air exchange in the box then any substrate will work good. a good air exchange would be,watering them say in the morning and all the water should be gone by nignt time. i myself use no bottom substrate. i use a plant or two. the plants are in everyway a window into to much water staying around. remember they only want to drink water not breath it all day.