how long is a piece of string ???
a colony can breed successfully with 9 males and 1 female.... especially if they have all grown up together and the alpha male has been established when the fish were smaller when they dont do as much physical damage to each other... once established the pecking order is respected later in life...
when you put different fish together at adult size you wont be as successful with 9m1f ratio thats for sure.... males will fight and very likely kill each other...
in my opinion with ancistrus the most productive ratio is simple 1m1f..... pairs produce more fry in the long run... as male doesnt get worn out tending to multiple spawns in succession... if you have 5 females get 5 males and put them in 5 tanks and you'll get more fry than 5 females and a male in 1 tank...