My water source is sand filtered. I'm not sure of the water temp in NC (warmer I think with the Gulf Stream), but the water here in So Cal only gets up to about 68 degrees in the summer. I don't think that any critters that live in and are used to that temp will manage to survive in my tank which is set at 80-82 degrees. That is just my theory, I don't know for sure. But if your water temp in NC is closer to the temp in your tank, planktonic animals making it through the filtration process might be able to proliferate in your tank. Filtration does not catch everything.