As long as you are only feeding the poultry food grit is not normally needed (although I haven't used pellets) however if you're going to be giving any sort of treats it's really best to stay on the safe side and provide it or let them have some access to the outdoors where they can find it themselves. Most feed stores carry poultry grit. I haven't used aquarium gravel as grit as it sometimes can have a coating or dyes on the outside and I've heard people say the gravel is too smooth to grind the food up properly. Anybody have any experience with it?