In the winter time in York PA. It gets about 30 degrees to about 7 degrees in the night, My question is does the heater on the hot tub need to be on with the pump or can the pump just run. I have a fox pool with the spa running off the pump and pool filter. Will the continuous moving water freeze without heat.

no, the continuously moving water will not freeze.

depending on how long and how low the temperature gets, even moving water can freeze... but it's gotta be cold and for quite a while