I started growing in hydroponics, about 35 years ago. Later, I switched to promix as its very forgiving and you can rebound from any mistakes. Coco is a bitch to use until you figure it all out- I know more people having problems with coco right now, it’s just crazy. I was a director of operations for a large garden store company, and access to promix was easy. And cheap. It’s just my preference and nothing really more. Why fix it if it ain’t broken?