I had a 4 ft x 11 ft raised brooder pen.
I raised guineas, chickens, ducks geese, and turkeys all together . I added them to the batch after they were a few days old. by then they are smart enough to not stand still and get stepped on. I rotated hatches so I was always adding more to the mix.
I had as many as 200 at a time..
when they got to a couple weeks old, they went into the nursery pens.
just don't put a swimming pool in for the ducks. some chicks could drown .
and ducks can drown , too , if they can't climb out of the swimming pool .
I found out that a guinea keet can swim if it has to..
for young ducks , you can give them a 9x11 cake pan to play in.. after they are a couple of weeks old, you can give them water deep enough for them to swim and dive.. but you have to be there to supervise.. keep the tub filled to the brim so they can get out by themselves.
I made a ramp for them to walk out and in on..the pool is a 2 foot x 3 foot x 8 inches deep mud mixing tub from our local building center store..much easier to dump the water out of to clean it than a kiddie pool..
........jiminwisc.......