After filling I have some left over osmocote. I end up using it as a top layer substrate.
I want to fill the 4x4 up with osmocote but I have just enought to do 1-1 1/2 inch of osmocote so I end up using soil for the bottom.
With the nutrients the nana will root into the osmocote
Im doing this for growing, not for showing. Once the plant grow to the size I want I will gel it down to wood or rock.