Agree Sawtooth 10-15 per acre but it all depends on what you are trying to achieve - 15/acre and many tell me I would not have a weed in my lake and that would kill the fish habitat. With 5/acre like I have stocked it I do not have excessive weed growth so that I have weeds lying on top, so I do not have stagnant water as the wind and and other things agitate the water, i.e. no mosquitos. These fish also thin the weeds adequately that my boat motor can get through so my family can enjoy the pontoon boat and our swimming area. The fishermen that come in tell me it is great fishing because there is some outstanding hiding spots and a lot of sunfish and bass breeding activity that there is great food for the larger fish to grow and fun fishing for kids.
So for those three criteria - no stagnant water, boat usage, and good fishing - I do not stock as heavy as is recommended. keep in mind though a lake that is not as deep as mine will have more growth and need more carp to attain these goals so it depends on the lay of the lake as well, i.e. depth, open to wind, is there an inlet and outlet, and many other factors that weigh on the decision.