My pool builder installed it and touted it as a "chlorine subsitute". NOT!! I was told I still had to shock, and I had endless green algae problems. After two seasons I gave up and went to a chlorine regimen, added 'quat algaecide and brushed once a week and it ended the problem.

My conclusion is that N2 is a scam. It did not do anything other than lighten my wallet by $90-100 a year.
Pete