My bet is you have more than one LMB in your pond... If you do, whether they eat all your SMB fingerlings or not, your pond is doomed to be a LMB only pond. SMB just cannot compete with LMB in a pond environment. Try to remove every LMB you can before they successfully spawn, but in the end... You may want to cut your losses, kill off all the fish and start over if you don't want a LMB pond...