Yeah they are more small pebbles, you can get an idea of the size of it compared to the crabs here
To be honest sitting on the little strip of rocks down the side of the pond seems to be their favourite spot, Im wondering if the rocks hold the heat so thats why they like it.
Annette
Carer of 5 Australian Land Hermit Crabs
Fili & Voldemort since 12/07/2011
Turbo since 29/09/2011
Frederickson & Kai 12/02/2012
and our new addition Stripey Ninja 25/10/2014
As for the question, its actually deeper than it looks. The substrate goes down below the edge if the timber you can see. It's actually about 3" or 8.5cm deep.
They are all still going strong :-)
Annette
Carer of 5 Australian Land Hermit Crabs
Fili & Voldemort since 12/07/2011
Turbo since 29/09/2011
Frederickson & Kai 12/02/2012
and our new addition Stripey Ninja 25/10/2014