Pino,
Picture the sand in a hour glass.........that is my "soil". Pure snow white fine sand that here they call sugar sand. Not quite sure why it is called that, the color is right but the sand here is very very fine. Not complaining though as it is pretty easy to amend if you have an unlimited supply of woodchips and thankfully I do. I do pay them in pellets..about 50 lbs of them a day right now:) During the off time when it is just the 21 adults they eat 50 lbs in about 2 weeks. They are good bug eaters but far as weeds they are no help at all. I guess if I did not feed them they would eat more weeds but they would grow much slower.