As we all know, birds need a Grit of various sizes to aid digestion. Without the ability to chew food the grit located in the gullet acts as a grinding force; in turn reducing feed to digestible size. I have suggested using Contractor Sand Mix (not play sand) with a variety of grit sizes. If you are lucky enough to have access to a small brook or active stream; you can scoop out containers of natural grit free of cost. Naturally the stream bed material has large stones mixed with the medium to tiny pebbles; so you need to sift the material. A hardwood square frame with window screen holes large enough for small grit to pass through is ideal to filter your final stage material. A local hardware store usually has wire screen or fabrics with various size holes to fit the bill. FREE is nice...so if you have access to a brook or stream, go that route.