So, all I have been using is the 3 way test kit and checking the pH and chlorine on my Intex 12x36 above ground pool. This has worked quite well until my levels dropped and now I am having to shock my pool to get rid of the algae. My question is, do I need one of the super expensive test kits to figure out what is going on? The chlorine reading on mine only goes from .6 to 5.0, so when I read about testing for "shock level" (which I still don't completely understand), do the more expensive test kits give a wider range of levels so I know when I have gone high enough without going too high? I don't at all understand what CYA levels are, but I know the expensive test kits will test that as well. Just trying to figure out if it is necessary to go get one or not so I don't waste money.