You are over-estimating your volume. It is more like 13,500 gallons. (Manufacturers always tell you it is more than it is because that appeals to people. The number they give is usually if the pool is 'running-over full.)

I'm assuming these testing numbers came from a pool store? You need to be able to test your own water. We recommend a Taylor K-2006 or 2006 which you can get from the test kit page in my signature below.

Don't worry about the phosphates. That is mostly just a way to get people to buy another product that they don't need -- a phosphate remover.

If your chlorine testing numbers are indeed correct, that means that you have a CC reading of 1.4 which is not good. To get rid of it, you need to maintain the chlorine at shock level which is based on your CYA level. (Please read the Best Guess Chlorine Chart in my signature.)

How does the water look, by the way? Still hazy? Is it green?

Your CYA is pretty high so you should not use any more stabilized chlorine meaning no trichlor pucks or dichlor shock powder. Just stick with plain, unscented household bleach. Generic is fine and is what most of use. In your pool, each quart of 6% bleach will add 1ppm of chlorine. A gallon will add 4ppm. Use that as a reference to help you figure out needed doses.

Get rid of the Nature 2. It adds metals to the water which causes a whole other set of problems. (One of the metals it adds is copper which is what causes blonde hair to turn green and stains pools.) We do not recommend the use of those units.

*IF* you have been using the Nature 2 unit for awhile, you might want to have a pool store test your water for metals before you shock it. Shocking a pool with metals can cause the metal to drop out of suspension and cause stains. If you do have metal in there, you'll need to use a metal sequestering product. We'll wait to see if it is needed before discussing that, though.

Hope this helps.