No, never put any in your fresh tank...it will take you forever to rid your tank of it....and anytiny bit of residual water left in there can freeze without doing any harm, it will have plenty of room to expand and will not apply any pressure to anything by expanding. Same applies to your grey and black holding tanks. Only reason put antifreeze in the holding tanks is to keep the valves from freezing and to keep them lubricated.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.