Hello, I received my first batch of chicks on April 7th, and I have 3 RIR's coming tomorrow, I just moved my 21 to a larger brooder (swimming pool) so that they have plenty of room, what kind of problems if any can I expect?
I don't think you should expect any problems. Almost 2 weeks ago I added 2 day old chicks to my 3 1/2 week old chicks. No problems whatsoever. I definitely would keep a close eye on everyone for the first day or two. Other than that be sure that your new little ones are eating and drinking. Good Luck!