If the stock tank is going to be above ground I think it will get to cold. The ground insulates a pond a lot during the winter. Did you plan on setting it into the ground?
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I am currently in the US Navy, so unfortunetly I have sold off my collection of herps. But over the years have kept many different species of turtles, geckos, lizards, amphibs, and even fish. Looking forward to getting back in the hobby once im out though!