I have found that it seems to work best if you don't change the water that often. I spend a huge amount of time making sure the new water matches the old water chemistry. For some reason, I always seem to lose a few shrimp when changing. I have never seen my cherry shrimp NOT breed under normal conditions. I have mine in a 20G planted tank with some java moss in there. Water temp 78, pH of 6.4, and soft.
Hope that helps.
Ryan
Boston, MA