I agree with Mitch.
IMO the best way to get breeding stock is to buy a group of juvies, from a reputable vender like COA, grow them out together and allow them to pair up on their own, usually at about 2 or 3 years old with Vieja.
For breeding Vieja it would be best to get the largest tank possible, and when a pair forms cordon them off from the others, (a tank of something around 300 gallons)
I have had Vieja spawn in tanks as small as 150 gallons, but they were the only 2 in tank.
Geo's are a bit easier, in that they can live as a group in something as small as 150 gallons, and when a pair forms, it can be move to a 75 or eve a 55 to spawn.