I concur with the majority here. I have found that the SMB will sustain themselves in the pond IF NO LMB ARE STOCKED. Look around on here how to make SMB spawning habitat, they will reproduce in a pond that is as deep as yours. They will have to be harvested once they start spawning just like LMB or they will over eat their food source - seen that happen before.

If you stock LMB, then the SMB and YP population will suffer. SMB because the LMB will out compete them for spawning habitat and the best places to hang out to feed, and the YP because the LMB can eat YP adults.