I don't think you need grit if they are on starter....but if you are going to feed them anything else like scraps or meal worms etc you should probably get them some chicken grit. For chicks ask the feed store for chick grit....I think it's #1 grit (and #2 is for full grown chickens).
In a pinch you could grab a box of parakeet grit to start them off but then I would switch to actual grit meant for chicks because parakeet grit may have too much calcium for them. I used a box for my chicks with no ill effects but after the box was gone I got them #1 grit. I also used coarse sand from a lake once but baked it in the oven in a pan to dry it out and kill off any weird lake bacteria that may have been in it...(but lets face it chickens dig through compost and poop and eat bugs off the ground, so germs probably don't matter all that much)..
They aren't born with any grit in their system - grit comes solely from them picking it up either from a container offered by you or their environment (for those who are out and about). The time when to start offering it will vary depending on who you ask - because it depends on when you intend to offer anything other than chick feed. They won't need grit as long as they are strictly on chick feed because they can digest that w/out grit - ANY food stuff other than chick feed, though, and they need grit. So, if you start offering "treats" (veggies, egg, etc) you need to provide them with grit....whether you do that at 1 week, 2 weeks, 6 weeks, etc is up to you.
IF you mix it (I prefer to offer separately free choice) you'll see recommended mixtures rates vary. MannaPro recommends 1 pound of grit to 40 pounds of feed, but that is just one example and ever brand or chicken keeper tends to have their own "formula"
Thank you. I started giving my 6 day old chicks some free choice chick grit. They only get chick starter now and probably won't give them any extras for at least another week. They need to get accustomed to their FF before I give them any dessert.
They were hard sells on it so I'm not giving them any excuses to reject it.
I didn't really think they were born with grit but I hadn't read they could eat starter w/o it either. I I made an extra trip to find chick grit because no one around me had it only to find it wasn't needed yet. oh well!