The tank cleaning cartridge arrived sooner than I expected and it is workig just fine.

Before I found these I was always replacing filters because they would look disgusting. Since I started using these cartridges my filters last longer and I'm saving a lot of money! And it's extremely easy to use. Just drop one in the tank! I would definitely recommend this product to anyone with a humidifier!

Product arrived quickly and was just as described. It was a replacement for one I had been using.

I used this with a new filter for less than a month and found that bacteria was present and the filter needed to be replaced. I will be using a liquid bacteriostat from now on.

Also confirming this information provided by another reviewer:

The description for this cartridge says that it "provides continuous protection against mold and bacteria" with its "Aquastat" antimicrobial technology. If you read the literature that comes with it, however, it says that it prevents microbe growth *in the cartridge*. Not in your humidifier. It's not an antimicrobial cartridge; it's a demineralization cartridge.

So far this product is doing it's job as expected. The tank is filled up with fresh water every night and it's still crystal clear. No mold or mildew or any other noticeable issues. So far no complaints from me!