Should I have grit available at all times for the chicks, or offer it to them say once or twice a week? It seems that whenever I put grit in the scratching tray for them, the eat it all. They love playing in it, dusting, scratching, and eating it, but I worry that if I put grit in with them everyday that they'll eat nothing but the grit. Do I give it to them in moderation now, and then leave it out for them all the time when they're older?