
I'm with you Erin on all the Betta's.At one time,I too had over 30-and then a pair spawned and had babies.It truely was a ton of work to keep up with-especially having all the regular tanks that I have.
I too think that 5 is a good number.Don't be fooled into thinking that females are not quite as aggresive as males either, for I've had more females be the meaner ones.
As mentioned,the most important thing is to introduce them into the tank all at one time.They might fight for a bit until they get a "pecking order",and then normally the tank does quiet down.
A big factor also, is alot of plants/hidey holes,so that each female does feel protected in her own space.
Good luck,and keep us posted with pics and such.