[Padres1234]

I don't know if I could pull this off but thought I would share with others. If anyone has any idea on how to achieve this post your ideas or thoughts here!

It looks like a cavern in the ground but you would need a very large substrate level to achieve this. Probably like 6" of substrate surrounding like a plastic circular divider or something.

 

[Yukiharu]

If I remember correctly the original picture is from a high-tech tank where the HC carpet "achieved liftoff" and detached from the substrate.
For achieving a 'cave' look you might want to consider using some sort of mesh or something and growing plants over it.

 

[Padres1234]

If I remember correctly the original picture is from a high-tech tank where the HC carpet "achieved liftoff" and detached from the substrate.
For achieving a 'cave' look you might want to consider using some sort of mesh or something and growing plants over it.

Ohhhhh, I see that now haha. Idk to me it still looks like it was grown on some rocks or something that was angled up which gives off the impression of a cavern down below.

 

[Yukiharu]

http://www.plantedtank.net/forums/29-substrate/219929-questions-ada-soil-hc-seperating.html original thread.
Anyway, an HC cavern is a neat idea and I think it could be done with mesh.