Phil Williamson wrote:
How deep should I make it?

[snip]
Depends on whether you have plants. If yes, it has to be deep enough to
let them root. Or you can put the plants in plastic pots and arrange the
decor to hide the pots. If you don't want to root the plants in sand,
you can make it as thin as you can.
Another thing is whether you have fish that like to dig. I must say I
don't know how frustrated diggers get when they can't indulge in their
favorite behaviour... cichlid experts out there?

Seb