i got some live sand to replace my ugly looking crushed coral/pebbles. the man at the lfs told me that i should go slowly with it, suggesting to replace the old bottom with the new sand 1/3 of the tank at a time. i was just going to push all of my rocks to one side of the tank, and take out crushed coral, and put the sand in, then repeat with the other side about 3 weeks later. will i harm anything by doing this? also was thinking about maybe scrubbing some algae off of the rocks at the same time. would this be safe? would just take a rock, put it in a 5 gal. bucket with old saltwater, and take a scrub brush to it. bad idea? thanks a lot.