I built a 20' long concrete pond. If you seal the pond with a below grade non toxic paint, leaching of lime is not a issue. You could also render it with a product like thorocoat(a thin plaster that is applied with a brush.)
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-Jake

1.1 juvie L.t. annulata
1.1 adult/subadult L.g. californiae
0.1 mexican double yellowheaded amazon parrot