10 hens with 1 rooster would be a happy cage if it's big enough. Think Hugh Hefner surrounded by bunnies. lol Not sure when egg fertility would begin to suffer because of high female count, though. I probably read it here but don't recall.
But density per cage is an issue to consider. I have Jumbo coturnix quail in a 30"x18"x18" bird cage tower in a spare bedroom. (The 18" tall cages are unboinkable for jumbos, if anyone was wondering.) One cage has 4 birds, the other has 5 birds in it. Those numbers include a male in each cage. More than one male and I'm sure they would fight. Bachelors in a cage simply crowed and crowed from lack of females until culled. My males with their females are happy and seldom crow unless wanting to show off for me.
5 jumbos is the most I feel comfortable with in a cage my size. 4 suits me better. I have to balance space limitations with M/F ratios. Males need more females but I like to see some air in their cages. I like to baby them, but they are not named nor are they pets. My indoor quails provide for our family and this works for me. Your goals may differ.
Also, I use Sweet PDZ (zeolite horse stall refresher) in the trays. (It dries the poop, but it also chemically neutralizes the smell.) I empty the trays weekly for cleaning. The cage with 5 really can't go much longer without becoming smelly. Being indoors, this is important. I also put apple cider vinegar in their rabbit water bottles every other time which helps. (I first scoop the PDZ with a cat litter scoop to get out the big stuff, then use a dedicated colander to remove little stuff.) Make sure your rabbit cage bottom wire is at least 1/2"x1/2" if you want coturnix. This is a must because their poop is big.
Open plastic shoe boxes make great sand bath boxes that retain the sand because of the tall sides although they do tip them over eventually. They also make great non spill feeders when you cut circles in the side and put the lid back on. My birds use them as a diving board into the sandbox. So funny!
Just be sure to keep one or two empty unassigned cages for the occasional need... giving a female a break... housing a few culls temporarily...figuring out which female is laying small eggs... weighing birds...or whatever comes up. And something always comes up. lol
So just decide what type of quail you want then find what stocking level you're comfortable with that meets your/their needs. The more air in a cage, the better. You can adjust and adapt as you go along.
I voted for jumbo coturnix and my comfortable stocking level worked out best at 108 to 135 sq inches per adult bird.
(That would be about 7 or 8 birds for your 30x30.)
Hope that helps.
