Not sure about safety, I've know people to use 10X recommenced with little ill effects, usually new stingrays. You could do a water change with lightly conditioned tap to balance it out. How big is the tank?
you could set up a filter with some cycled bio media on a holding tank. Then the water would nitrates instead of ammonia, hopefully less mitrates then the water in the tank. If this is a long term thing you will have to deal with i would contact the filter guys. They can set you up with a cuctum system that will do what you need since you probably don't want to get a full RO/DI system because the water is too pure.
thats what I'm hoping-the water company came to the house today and collected a sample, and they will be testing it next week, and I'll get the results in the mail...the people I spoke with in the lab said that the chemists are already aware of my findings...hopfully this doesn't take forever!
i am not a ray guy so I know nothing. With that said my water has been 1ppm for 2 years, for 2 years I do a 50%wc each week and I don't notice the ammonia the next day. So Logic would seem that if you do a 50% each day the ammonia from the previous day should be gone by the time you do the next change. Plus prime last 24 hours so it should be bound by the time its consumed.