sounds like you have a pair!
the 29 is ok for the pair. the other convicts left over will be beatin up though. i had a pair in a 30 gal, and they would even bite my hand if i got close to their spawn. in the place they are cleaning out, they probably will lay eggs. when i had a pair, they moved the eggs to several different spots in the tank. do you have another tank for the fry?? they will breed alot! you can tell when there is a pair cuz there will be a male nd female guarding the nest, and the other cons will probably be pinned in a corner and constantly being picked on. i didnt even know my convicts spawned until i turned over a shell and there were a bunch of eggs on the inside of it!! the female was also bitting me and i had no clue why untill i saw i was holding a shell filled with little eggs