I do have to share my experiences. I got my Gymno Balzanis from Jeff Rapps, Tangled Up in Cichlids (highly reccomend him). My male balzani went after the one female and before I could seperate them he had killed her. The remaining female was left alone. Until I went away for a few days. The other female was finally killed also. Apparently, the Balzanis should be kept in groups of 5 or more if you're gonna keep a male. I am only sharing my experiences. I am sure there are tons of good experiences also. I had them in a 90g with dither fish. Not sure if this was an isolated incident or not. However, after reading a bit more I found out about the male being a PITA in the tank. I love the Geo and Gymno species.
With Gymnos, it is best to have at least 3-4 females to every 1 male.
You could start with 10 to 12 fry, then trade the excess in when you get a compatible group.
I find for the Geo altifrons group one needs a much larger tank in the end, at least 100 gallons.