Originally Posted by Luimeril
x: noooooooo. that's way too small to keep that many females. minimum size for a group, is 4~6 in a 10 gallon. x: you can keep ONE in a tank that size, but that's it.
I wouldn't do less than six but you CAN do six in anything over 8 gallons.
I find the ten to be a little tight with 12
You can get away with six girls if you add a pair of bloodfin or other such pair-happy fish. My girls have always gotten along well with a male guppy, male mollys, the bloodfins and most female guppies. I had one girl guppy get to over 3 inches in size and she became dominant fish.
But back to the question. A five gallon tank should never be used for any multiple fish that add up to over five inches. Each girl full grown is 2 inches, so you could have two and a half betta girls in a 5.5. Which is exactly what you'd have if you put in 3.