I'd toss at least a couple hundred HBG in there. Make durn sure that the LMB are properly sexed, and yes, I think the only way to be 100% sure is to catch them before they drop their eggs and check that way.

You might want to put in 25 RES too. They'll help control any snails that would be a host to parasitic grubs. (white, yellow or black) They don't reproduce near as much as BG.

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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).