Some people bred a single pair of germans in a 10 gallon tank ... but I wouldn't recommend it and deffinately would never try it. Bolivans just get way to large to have a pair in that tank, I wouldn't even do one unless it was a quarentine tank.
I'd do a pair of german blue rams in a normal 20H gallon, but I won't force a pair of bolivians in anything less than a 20 Long. They get twice the length and more than twice the mass of germans.