HELP!! What Did I Do?!??!

[BCOrchidGuy]

Bev, I'm not sure if salinity has much to do with ammonia levels but pH does, if your pH dropped rapidly ammonia wouldn't have been a problem however if your pH went up for some reason, ammonia becomes more toxic as the pH rises. Any chance there was dead material under the "cyano" that could have released some nasty gasses? I think a pH crash would have occured through but I'm not sure. That being said, it's a large tank so I would assume you didn't remove enough crud to do that. If those snails had died under the rocks they could have been the problem, and when a snail dies there is lots of black crud as they decompose remember they are almost all protein and they decompose fast.
Glad to hear things are clearing up. Here's to the end of disasters in the reef tanks. (clink)

Doug