He first became intrigued by sphagnum moss after reading about injured World War I soldiers whose wounds were packed with moss had greater survival than those whose wounds were packed with cotton.
"I knew from my years working with wound healing that it had to be antimicrobial," Knighton said.
His first interest was in medical applications, but Knighton, who is also a pilot, suspected that the moss might be helpful in conditioning water after flying northward over Minnesota's many lakes.
"As I went north, they got cleaner and cleaner," he said. "I wondered: 'Well, maybe it's the moss?'"
Frustrated that he could not keep his home spa chlorine levels stable, he tossed some sterilized moss in. "Within ten days, it cleaned up the spa."
The moss readily absorbs heavy metals, including iron, which often encourages microbial growth. Without any iron in the water, microbes can't grow.
But, more importantly, Knighton says, the moss also prevents the growth of biofilm, mats of bacteria that stick to pool surfaces and coat the inside of pipes, causing corrosion.