Is it ok to leave my new N2 cartridge in the system and still begin using grocery store chemicals? It seems that the pool has been easier to maintain since I got the N2 cartride three years ago, and I had just got a new one, before I found this site. Well, I am curious, I want to try to save a few dollars and just use the store bought chemicals. But, as seen HERE, it says that you should not do this if you use the N2 system. If the chemicals are the same, then why couldn't I?