I had crushed corals on my old system... had a bad experience with it cuz detrius would get stuck and I was too lazy to clean it. I'd have high nitrates(40ppm and above)... that's why I had a de-nitrator hooked up on that system just to keep nitrates low...
Sand was never a problem for me, it always kept things in check.
I went BB on my current cube setup and it's doing well for me too