>But if it de-gases inside a fish -- symptoms similar to the "bends" of >deep-sea divers can occur. That is the dangerous part. The fish, >usually, do not die right away, but are impaired. Some make it, other >don't. Are there visible symptoms? What I'm digging for here is, can I tell if or when a water change is inflicting this kind of suffering on my fish? Alysoun McLaughlin