It's Early, but I'm already thinking about winter

DONT put the antifreeze in the fresh tank and run it out of there. The previous owner did that to mine and it took hours to get it all out. See also, fill, drain, fill, drain, fill, drain, fill, drain...

Drain the fresh tank completely and leave it. Then use the suction port on the pump to only run antifreeze through the pump and lines. Make sure you drain the water heater and bypass it as well or you will be flushing it over and over to get the antifreeze out of it too.