I use it in three of my tanks because I have no alternative. Ceramic rings won't fit in the itty bitty cartridges. I change mine out every few months. And sometimes I will rinse them really good in tap water (a big no-no if the cartridge is the only form of filtration but all of my filters have a sponge also) to get all of the gunky stuff off instead of just replacing them. Some filters you need to use the pre-packaged cartridges, in some there is enough room to fill a mesh bag and put it in there (but if you had that option, I'd just put in ceramic rings), and others have baskets that you fill with carbon (I would also just put in ceramic rings).