Shrimp need a fully cycled the tank (and I would say beyond fully cycled, like the tank has been up and running with fish making deposits to balance the tank ecology before putting in shrimp). They are also real sensitive to water additives like water dechlorinators. I only use water from established fish tanks for the shrimp to avoid any complications. However, I do have one tank that seems to support shrimp for maybe a month and then suddenly all the shrimp disappear (I never see any dead bodies, but there is a cloud of algae I purposes put in there for the shrimp to eat and I figure they go under there and die, same algae I put in the other shrimp tanks with no problem)--no predators, nothing new in there. The shrimp in all the other tanks are thriving and, as far as I can tell, nothing is different about the death tank except it doesn't seem to be able to support shrimp life including scuds.