I'm getting some delivered today.Algaebarn started selling it recently. I've had nothing but good interactions with them so I'd be surprised if they backed a product that didn't do anything.
https://www.algaebarn.com/shop/aquarium-supplies/coralline-algae-bottle/
ARC reef who I think is the originator of Coralline in bottle, has these bottles available on their website at a lower cost (16.99) vs AlgaeBarn (22.00).
https://arcreef.com/
I ordered 3 from ARC reef just to give it a try.
Covering the rocks with many different corals looks much much better than purple rocksI like how rocks look covered with it.