thanks for all the help.
mrzoggs: I should have used eco earth because it is softer. the top soil gave me some splinters, but it shouldnt harm my frog because I will be growing moss over the topsoil anyways. made my moss milkshake today and painted it on. it should be done in about two weeks and the background should be completely covered in moss.
If I need to do the background again I will just buy the eco earth that comes in a bag (instead of a brick) and apply that