Do not freeze Forget About It For Boats.
The patented blend of probiotic bacterias are very resilient under most conditions but we consider it best practice to not allow the bottle to freeze. It may not kill it directly, but we believe it could reduce its effectiveness. It will last the longest in the bottle when stored at near room temperature. Heat does not seem to adversely affect it. In some climates the effluent in the holding tank is going to freeze. Freezing will cause it to go into suspension until the effluent thaws allowing the consuming and cleaning activity to restart.