i have a chunk about as big as my daughter's head that i've had since day one - totally covered in coralline and grape calerpa. it's about 8 or 9 lbs. it's stacked between one rock and a rock that has my mammoth colt coral on it. my colt coral is starting to get caught in my overflow, so by getting rid of that chunk, my colt will have a bit more room. remind me of it if you're over again.