Whole tank died over night...

[Pure]

Naa in small quantities like that there is little it can do to harm any one. Nothing a normal water change can't dilute. The leaching of toxins or what ever, has been linked to certain diseases like HTH with fish such as discus.

In this case it was more of a stab in the dark, as I really don't even know if he even uses carbon. But it's the best I can do with what I have to go on.

 

[blade_pride]

I really doubt this is it, but by any chance did you have a Cold or Hot spike. With it being at the edge of spring the temp outside is real un-predictable. Its running 85-89 in the day here and as low as 30 at night, its playing hell on my AC.