Just a thought, if there is another pool store close that could testCYA, that would be interesting......
I think you can see, those pool guys are full of you-know-what. First, CYA does not destroy cartridges. What a horrible statement that was. Dead chlorine....funny, my understanding of chlorine is generally it's either a colorless gas, or in liquid state it's liquid, not solid, particularly in water it could NOT be a solid. Furthermore, reading though here you will find that generally it's an infection in your pool that makes the water cloudy, and that algae when it is dead settles to the bottom of a pool.....not chlorine. Again, I believe we are at strike two or three for your pool store........I would not believe a single thing they say again about a pool......Ok, maybe the color of a pool they sell, that's it.
Take your "oxidizer" back later this week (tell him you dumped the pool or didn't need it after all) and again I repeat....you only need bleach to keep your pool clean and sparkling.....it IS the ONLY sanatizer you will ever need.
What did you learn today? I hope you learned that it looks like your testing methods ARE correct (congratulations, and yes, it took me awhile to get there too), and now, you need to be absolutely certain and confident you know how to use the pool calculator. Remember you will put what your testing results are in whatever block you are trying to use AND you must put in the target level you are going for. Next week I should be able to ask you how many ounces of bleach you need to add if your chlorine level is 2ppm and you want to bring it up to 7ppm (assuming your target is 7 for your pool). In the past two months I have had my pool up and running and using the calculator, I can now do that......I know, kind of amazed myself I can do that, but that is the familiarity you will get using the pool calculator and doing your own pool maintenance.
If you're certain you cannot maintain your clorine level, then you really do have very little CYA or you have a heck of an infection in your pool which it seems you are winning, eating chlorine. I would (and other here will too) put half the amount of CYA in your pool in a sock and let it dissolve for a week, then retest after that.
If your algae is dropping to the bottom you will have to invent a vacuum for your pool or stir it up alot by brushing the floor and try to get the Intex filter to capture the dead stuff.
Keep it up, your just about to have the best looking pool in the neighborhood, despite being screwed up by the pool store!!
Bob E.