Very nice! Love the substrate - what is it?
I was going to reply with that very question. I usually like solid color substrate. Even if it's an unnatural color such as purple or blue, I prefer it to be solid.
But this is really cool.
Is it a custom mix you made or did it come prepackaged?
And the rest of the tank.... super nice. It's nicely balanced with just the amount of decor.
I agree too about the background. Put a black (or brown that matches the brown color in the substrate) background on the tank and I think that would put it over the top.