I'm not saying some people don't need it. Some stuff I've read makes it seem like the in thing to do. I was only bringing up the topic for discussion because I'm guessing there are people using it who may not need to. Also people just getting into the hobby might read somewhere they need to use it. I had read on a different site when someone asked what they needed to set up a small freshwater aquarium some guy told him to use ro/di water because that's what he used in all his tanks. He didn't tell the person to test his water and if it has high nitrates or any other problems to get a ro/di system