A sad, sad day for FishyFishy

[FishyFishy!]

The Mysis is the only thing that I can think of. Thats the only thing that was introduced into the two tanks the night before. Brand new package, no previous signs of disease or stress from fish, water perams are perfect, and killed all fish and nothing else.

How would I go about testing? Not that I really need too, because the worst has already happened, but it would be nice to find out.

I will from now on thaw and wash all mysis before feeding thats for sure. I used to just let it get mooshy then drop it in.