Initially I would start out with something along the lines of 45% SMB, 45% HSB, and 10% LMB.

Then get on a program (or raise your own) where you stock a handful of SMB and HSB every year.

Also if you want to help your smallies compete, feed them high protein pellets. Native SMB will take to pellets much faster than native LMB.

What happens is the LMB will take the prime feeding areas in the pond and in a pond there arent too many of them to begin with. By supplementally feeding the SMB pellets you give the upper hand back to them!