When I bought Flourite at the nearby chain pet store I was under the impression it was basically mineralized dirt that would release nutrients to the plants over time. Now I find out it's basically smashed up terracotta pots. Sure it may release some nutrients over time. But it is far from being an ideal substrate for plants. All rocks, by definition, contain minerals. But you don't see plants growing in gravel beds. My next tank, and all future tanks, will be dirt. That's what plants need. Even wild aquatic plants grow in dirt at the bottom of whatever pond or stream they are in.