First, make sure the shrimp is dead. Molting shrimp may stay still for long periods of time and are often mistaken for dead shrimp. If the shrimp is a pink fleshy color and on its side, it’s dead.
Usually, random deaths are caused by one of three things: ammonia, water changes, and trace metals.
Ammonia is self-explanatory; shrimp are very sensitive and can’t handle ammonia present in the water.
Although water changes aren’t a bad thing, water changes more than 30% can induce molting in shrimp. Molting itself isn’t a bad thing, however, if the KH or GH in the water is off the shrimp (especially caridina) may fail to molt, leading in the shrimp dying. This is mainly an issue in the first few generations of shrimp, as shrimp after that are more accustomed to the water conditions. To prevent this, don’t do water changes more than 30% and we recommend RODI water for caridina shrimp.
Shrimp are very sensitive to trace metals, and often times trace metals end up in the water, which kills the shrimp. Most times, this is through fertilizers and medicines that aren’t shrimp safe.
Sometimes, though uncommon, trace metals come from very old boilers that leech metals into the hot water. To avoid this, use RODI water or cold tap water and let it heat up with a heater.