A death that follows the same event every time is evidence, not bad luck. When shrimp die within hours of a water change, repeatedly, the investigation starts with the bucket, not the shrimp: something about the incoming water, or the way it goes in, is hitting animals that were feeding and moulting normally the day before. Shrimp are far less forgiving of sudden change than most fish, and a water change is the single biggest deliberate change a tank ever gets.
The usual culprits hiding in fresh water
Temperature mismatch is the simplest: new water several degrees cooler poured in at once can shock shrimp into a fatal emergency moult. Chlorine and chloramine come next — both are added to tap water to make it safe for people, both are toxic to shrimp, and chloramine in particular is not removed by letting water stand; it needs a conditioner that neutralises it. The third culprit is a chemistry swing: shrimp live inside a shell they must periodically shed, and a sudden shift in pH or in the water's mineral content can trigger a moult they cannot complete, the classic white ring of separation behind the head being the visible sign. Old copper plumbing is a quieter suspect, because shrimp are exceptionally sensitive to copper that fish tolerate without complaint.
Changing water the way shrimp can handle
Shrink the change and slow it down. Smaller changes, done a little more often, move the chemistry in steps shrimp can follow instead of one weekly jolt. Prepare the water in advance: neutralise chlorine and chloramine, then let it come to the tank's temperature, or warm it to match before it goes near the tank. Add it back gradually — a slow trickle through a length of airline tubing over an hour or two is the method many shrimp keepers swear by, because the tank's parameters drift gently rather than snapping. Avoid stirring the substrate deeply during shrimp-tank changes, since disturbed mulm can release a pulse of waste into a small water volume.
Test the pattern before you blame the shrimp
Run the comparison deliberately: test the tank water and a sample of your prepared change water side by side for temperature, pH and, if your kit covers it, general and carbonate hardness. A gap in any of them, found on paper, explains deaths that looked mysterious in the tank. Then change one variable at a time across successive changes — matched temperature first, say, then slower addition — so that when the deaths stop you know which fix did it rather than guessing among five.
When the pattern refuses to break
If shrimp keep dying after changes despite matched, treated, slowly added water, widen the search: something in the source water itself, a contaminant on hands or equipment, or a problem in the tank that the change merely exposes. At that point take your written record to an aquatic veterinarian or an experienced invertebrate specialist, because a dated log of what was changed, when deaths followed and which fixes were tried is exactly the evidence that lets them help quickly — and keeping that log in the colony's Pet Passport on KinsLe means every change and every loss is already in one place when you need to show it.