We have three Indian Runner ducklings. One is 3 days old. One is about 10 days old. One is 3-4 weeks old. Right now they are in a small container, but they need something bigger ASAP. Tomorrow we are building a bigger brooder for them. How big should it be to get them to 6 weeks when we can put them out with the chickens and Cayuga pair? We don't want to put them out one at a time. How warm should we keep it? Obviously, the 3-4 week old doesn't need the heat. Thanks!