Sorry to hear of your incident, but I doubt that the ChemiClean was the dirrect cause of your coral bleaching. There were most likely a number of factors involved in the ordeal (water quality, temperature, water motion/disolved oxygen levels or a lack thereof). The label says to do a 25% water change after dosing. Unfortunately it does not tell you to suck out most of the Cyano before dosing, which is what I tell all my customers that I prescribe it to. Anytime algae/bacteria, or anything dies it uses up oxygen hence the increase in redox levels. If there is a lot of the slime algae in the tank the oxyen consumption can be astronimical. If you had a redox meter on your tank I'm sure the value would have greatly increased.
If used correctly it is a great product. I have used it twice in my 120 reef. The first time was for a massive kill off, but I only had liverock in the tank so I didn't bother to suck most of it out. The second time I used it was after the tank had been establised with many SPS corals (elkhorn montipora, M. capricornis, A. tortuosa, 2 species of tricolor acropora, A. millepora, Acropora sp. "blue tip", and Seriatopora sp.), a few gorgonians, some cool zoanthids, a couple of LPS corals, pulsing Xenia, shrooms, star polyps, etc. etc. I lost none of them, nor did any of them react to the presence of the ChemiClean. I did however, suck out as much of the "slime" as I could before dosing with it.
I wouldn't be so quick to knock the stuff.
As far as using erthromycin to kill off the "slime", I don't recomend doing it in a reef tank or any tank moderately to heavily populated. It is a strong antibiotic that has proven to be very harsh on nitrifying and denitrifying bacteria (i.e. the biological filter system). In short, it can REALLY mess up a reef system that relies on the nitrifying and denitrifying bacteria to function properly.
Unless you have the knowledge and are equiped to handle severe durress on the system and still come out of it on top. Don't use erthromycin to kill the "slime".
Just make sure you have sufficient water flow to keep up the dissolved oxygen levels and many potentialy "leathal" incedents can be avoided.
I always suggest a minimum of 15 times the aquarium's gallon capacity as a minimum total flow rate (all pumps in tank added together). I run about 6000 gph in my 120 (give or take depending on what powerheads the wavemaker has on or off).
Again, sorry for your loss.