The idea is that the cage will be large enough diameter that with the heat source in the center, everything outside the cage will be inhospitable for the tilapia sooner or later. After all, a livestock tank de-icer is not going to heat the whole pond. At some point the pond will be cold enough that they will move inside the cage to be in the warmest water possible. That is when I make my harvest.

�That boy, I say, that boy's about as sharp as a bowling ball�