if you use vinager, there are no worries about chlorine from bleach or muric acid.
i dilute my vinager when soaking (usually overnight or longer). can also store and reuse the vinager. the solution is a little funky looking, but will work for many more powerheads. i will reuse many times before pouring down the drain. after done toothbrushing, i give a good rinse and dry. usually have a couple powerheads laying around, so they don't go straightback into the tank.