I don't know if threadfins will sustain themselves in a 1/3 ac pond.... I was under the impression (possibly mistakenly) that they needed more water to help mitigate rapid temp changes, plus a larger BOW can be deeper to add more water volume which also helps slow down fast water temp changes.

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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).