freezing water falls

Question
i have an 800 gallon  water fall in my backyard.  The reservoir holds about 600 gallons.  the cold Missouri winters is freezing most of the water.  i have very little water flowing at this point.  is there anything i can do or add to the water so that it doesn't freeze.  im concerned that I'll burn up the pump once all the water freezes.  what do you recommend?  thanks

Answer
Hello Sam!
First I would like to apologize that you had to wait so long.
Evidently AllExperts had some problems with getting this question to me and I could not access it until today.
You could try adding some solar or kosher salt. This will not hurt the fish (other types of salt can hurt the fish because they have additives that are poisonous to them. About 1 pound of solar of kosher salt should not hurt your plants either and might help to keep that waterfall flowing better.