Thanks for all the pointers. It's slow going, but the tank is coming
clean. I've blown all the buildup off the rock and suctioned that out of
the tank, as well as scraped the sides down. I used a small fish net to
sift the cyano off the top layer of sand.

I did a 10g water change yesterday (it's a 65g tank) and will do another
10g today. Water parameters were whacked out yesterday morning, but are
more inline today with the replacement of media bags, cleaning of
detrius filters and addition of trace elements. Calcium is low, but I've
added some kalkwasser and will test again tomorrow.

All of the coral colonies are dead or nearly so. There's a couple button
polyps still left and one lonely mushroom, but that's it - a loss of
about $500. I hesitate to add any cleaup crew (shrimp or crabs) until
the tank settles bak in.

Thanks again for your help.

mark h