It's highly dependant on where they are caught, and who the collector is. For instance, I know that there is still a lot of cyanide used in teh Phillipines and Indonesia, especially by poorer people. In truth, you can never be sure just how a fish was collected, unless the dealer selling them has collected them himself and is reputable.
As for Flame Angels, most are collected in the Hawaiian islands, and are net-caught. From what I understand, those caught in the Marshals and Christmas Island are sometimes caught with cyanide by "bummers" (people form other palces that travel to those areas specifically to "poach", then sell as lowest price to distributers). If you can, get Hawaiian Flames. They aren't as red as those from Xmas Island (they'll have more yellow to their flanks), but they are much more dependable.
I've actually found (through experience and anecdotes from others) that the Dwarf Cherub Angel are the most hardy, as are the Ebliis. Lemon Peels are beautiful!
