I get asked about this at least 50x every fall
And I'm always baffled by it. Why would anyone would worry about keeping K.O. alive in the tank through the winter??? 'Cuz if the antifreeze doesn't kill it, freezing will. K.O. isn't like a yeast starter...you don't start it working once and that's it forever. The tank should be at least nominally rinsed after every pumpout or dumping at sea...and thoroughly flushed out several times a season--which requires starting K.O. in again. At the end of the season, it should be VERY thoroughly flushed out...even with a little detergent...pumped out (and thoroughly rinsed out if you do use any detergent)...and antifreeze added. By then, there won't be any K.O. left in the tank to worry about. In the spring, all the antifreeze should be thoroughly flushed out again...and K.O. added. And btw, the same procedure should be followed no matter what you use in the tank...clean out the tank at the end of the season...clean all the antifreeze out in the spring.
