A while back I had an outbreak of white spot syndrome virus. It looks like ich with little white dots on the exoskeleton but they are just calcium deposits. The virus acts internally, from what I've found, it's known in the shrimp culture industry, but not so much in the aquarium trade. I read that it has a 100% kill rate if it is contracted and a 90% chance of contracting it if it's present in the water.
My shrimp developed the spots, then about 2 weeks later did emergency moults (probably a reaction to the exoskeleton infection. About a week after that they became very crippled and disfigured and died soon after. I never found a cure and it wiped out my tank of shrimp. Didn't affect the fish at all.
I was just wondering if anyone else has dealt with this.
