If I were you I would siphon out the crushed coral and the sand, and replace it with new sand. Use a siphon hose (1/2 - 5/8" should work fine) and suck out the full depth of sand/CC. Do 1/4 at a time, for 4 weeks. Remove 1/4 and replace with new sand that day so the edges of the old sand aren't exposed. Just make sure you do the full depth in one go (don't suck out the top layer one week then the next layer the next week). Know what I mean?
The idea is to prevent anaerobic areas from becoming aerobic (which kills that area and will create ammonia spike), and to prevent getting noxious areas into the water column. Doing it over 4 weeks allows the critters in the old sand to populate the new sand.
I'd also suggest you have some Prime or AmQuel on hand, and put a SeaChem Ammonia Alert badge in the tank for the weeks while you're changing out the sand.
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~ Mindy
SPS fanatic.
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