Bummer on the R0871. Hate to stop now so If it were me, Id got back to the pool store with a sample and let them test. Be sure to take the sample directly there and keep it in the shade. If they sell Taylor chemicals, you may get lucky (extremely lucky) and they have R0871. It appears you have the "biofilm" problem Ben mentioned (see Waterbears post above). Problem is, without a good test method and 0 CYA and no way to test I don't know exactly how to advise. You must keep the FC between 10 and 15 in order to beat this. Yo Yoing won't do anything but feed the bio and cost you money. You are going to be using up chlorine FAST with the "bio" and the UV. You should probably buy the chepo kit if you can't get R0871 and use "Carl's patented shot glass method" of testing which is basically diluting the samples with distilled water to make a tester that was intended to test up to 5ppm to test higher. Use a 1 part pool water to 3 parts distilled water and see what happens. If the test reads 4 you have 16ppm. Only problem is that most of these only test for TC and cannot determine FC or CC which is really what you need. Hope the pool store is close....