You'll get tons of pods, little micro things you'll start seeing on the glass, mini brittle stars (Which will reproduce like mad in your system esp w/o fish to eat them), and TONS of beneficial and diverse (I'm sure) bacteria that will help keep your system stable as it'll seed your tank. The Rubble is just what it sounds like, fragments of LR. The crud/mud though is messy and I suggest putting it in your refugium or back of your tank as it'll make your tank not look as 'nice'.