If you're a boater or have ever walked a marina dock, sat on the back deck or cockpit of someone's boat, you've most likely had the occasion to inhale the odiferous and unpleasant aroma coming from the vent of a black water holding tank as someone flushed their business down the boat's toilet. I came across a solution a couple of years back and I've just installed it on our Ranger Tug. It helps us, our guests, and dock neighbors not be bothered by disagreeable odors. The product I installed is an inline, charcoal-activated, holding tank vent filter called SaniGard.…