So I've had my pool about a year now and when I did the in person pool school through my local Leslie's, I asked about this small grey piece on my equipment pad. He told me I didn't need to worry about it. I got to looking at it today, and it says it is a mineral purifier. The thing is empty right now, but I have been trying to find a replacement cartridge for it, thinking maybe it could help me keep my pool cleaner. However, I'm not really sure how it works or what it does. If it is something that would be useful in helping keep my pool clean and my costs down, I would love to purchase a replacement cartridge. Only problem is, the serial number is completely rubbed off the sticker on the side of it. So, I'm wondering if someone can tell me what it does, if it's useful, and if so, where I can find a replacement cartridge for it? All I can seem to find are the vessels, and I just need the cartridge. Thank you!