sorry, was looking for a breeding thread for you but i can't find it. i'd rather you hear about breeding from the horse's mouth.
you could probably keep the rhom in a 29 gallon for quite awhile. i had mine in a 20 for atleast 4-6 months but it didn't seem like it was growing. 3 weeks after putting it in the 75, it put on an inch. i didn't measure it at all when it was in the 20 so it could just be a case of me looking at it everyday and not noticing it grow...everyone visitor said it was getting bigger but i didn't see it. i can def tell it's growing in the 75 though.