Here's what I recommend you do.

Now, spray the area that you are feeding the fish at with Aquathol K or Aquathol Super K, then in February if the pond doesn't have flow through water I would treat the whole pond with a 10 PPB dose of Fluridone (Sonar A.S.)

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).