Hi! I'm a new chick owner--have had two grown chickens for two months but our chicks arrived yesterday. We have six and they are a week old. My friend tried to get us more but several died and we ended up with only a few. SO, today I ordered my very own chicks on Mcmurray and they will arrive next week. 25 of them. Here is my question. Can I put the new chicks in with the old chicks when the new ones are one week old and the older ones are three and a half weeks old? Do I have to start a whole new brooder? Also, when do they no longer need the lamp? I heard three weeks old but didn't know if that was true. If it is, I suppose the old ones will be too old for the temperature the new ones will need? Any help would be greatly appreciated!