The only practical way to lower it is to drain and refill. There is a chemical that pool stores sometimes recommend that you use to lower it, but it is melamine--the same thing that you use in the CYA tests. It will turn your pool milky white, then you have to figure out how to get it out.

If your pool is in sun all day, you might require a higher stabilizer level than some, but 150 is too high for any pool. Mine is in full sun all day in Louisiana, but I only run mine at 80-90, and I think I keep mine higher than most everyone else on the board.

Janet