My pool guy had recommended this stuff to me and offered me a discount on weekly service if I let him use it in my pool. He charged me $90 a year for the PoolRx (which he didn't name, he just called it a "mineral treatment" and I later found out what it was) and discounted my service $10 per month, so it was a net savings for me, it made his job easier, and now I see it probably saved him money on chlorine, too. I later took over the pool maintenance on my own to save money and looked for advice online. I found a very knowledgeable community on a certain website that was full of great advice and pool care tips, but some of the more vocal, condescending members of the forum were very against using any type of mineral additives like Pool Rx and would ridicule anyone that said they were going to. It seemed that more than anything they were stuck in their ways, but they had some credibility and made some plausible arguments against it, so I followed the advice and was using only liquid chlorine to sanitize and keep algae at bay. I was having to shock my pool a lot more than I had liked and the algae still appeared in some areas even though I was keeping my pool at 5 ppm chlorine most of the time. That's higher than I wanted to keep levels at but algae would get bad if I didn't (and yes, stabilizer and Ph were ON POINT). I was going through a lot of chlorine. After about a year of this, I said the heck with it and bought the Pool Rx. Huge difference, right away. I bought the 7.5-20K gallon size for my 22K gallon pool because that was what my pool guy had used. It has worked great and I have had no algae and no problems with chlorine levels kept at 1-1.5 ppm through the hottest 4 months of a Phoenix summer. Chlorine has even dropped to 0.5 ppm a couple of times when I had to go longer than normal between servicing it, but I still had no problems. I have not experienced any of the negatives that the "experts" had warned about. No increased scaling or staining, no green hair, no problems with the pump or equipment. Just clear water, a pool that is easier to maintain, and a pretty good savings on chlorine. I added this canister in May and I plan to add the booster in October, then I'm starting over with another canister next May.