Dead fish

[inboysandvoodoo]

I don't understand, I've lost all my cardinal tetras in the last few days, checked water with test strip and has came back all fine. Also have hatchets one died last week but rest are fine, treated water with disease away, no sign of white spot or fin rot... Any ideas?

 

[IHaveAquariums]

How big is the tank? What are the parameters according to the strips? Also strips are notorious for being off a bit. How long has the tank been cycled? Tank mates? How many? Need more info lol