Note that any of those "sharp" edges with the soil will disappear with water - soil is slippery stuff
& a good thing too as it means a more natural slope shape will appear
If you want rockwork to look more "natural" pay attention to the strata lines - they should flow same direction, especially if rocks are stacked in a particular shape, tumbled rocks will/may vary more in strata lines
- but then I prefer the rock style of this tank
Mighty Cave
You may have a very different view in mind
If you look at the rock scape packages at Buce Plant, they do a fair bit of mixing up of strata lines
As you're doing an Iwagumi, you may want to look at effects of water & light on the stone colours as well
Bleaching the seiryu type stone will usually return them to more until form oxidation (color) state - if that's your preference
It's fantastic to see soil & rock in this tank