I've read that betta owners should have "PP" on hand, but that's the last time I've heard anything about it. I've learned that "PP" is Potassium Permangate, but that doesn't answer the question! I haven't seen it for sale in the LFS, and I've never seen any instruction on what it's used for & how to use it.
My next question was: what should I use to sanitize my tanks/filters/decor for storage?
I consolodated my fish into "only" 3 tanks (down from 6). One of the tanks is a 10-gallon that I used as a spawn tank, but the spawn failed. I pretty much decidded to soak it with a few drops of bleach (which destroys everyhting it touches, too).
PP is generally only used as a last resort treatment I believe. Many people prefer to try more natural treatments such as aq salt, epsom salts, banana leaf extract, IAL etc. Generally it is best to try natural treatment first and then move on to medications if the natural way does not work.