The answer is "it depends". It depends on how much food they have to eat. I stocked TGC in different ponds at a clients place. One pond had lots of plants, the other one didn't. Even though the pond with lots of plants has 3x the TGC as the other one, it's TGC are still almost twice as big.

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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).