I love the look of it and that it's said to hold it form for years rather than ever break down. For my purposes I do wish it buffered KH and pH acidic, but to best of my knowledge it's inert. I'd even give it a shot in my inert set ups, but last time I checked it was only available in 5 pound bags and I don't have small aquariums. If they ever start offering it in 25 pound bags at a better price per pound I'm eager to give it a try. Seems the BB shaped spheres would be less likely to pack down like other clay based substrates I use such as EC and Flourite.
Nothing good happens fast in an ecosystem.