Why are shrimp dying after a water change?

Why this happens

Shrimp regulate water and ions across their body surface and gills. A rapid change in conductivity, GH, KH, pH or temperature can create osmotic stress, while chlorine, copper or pesticide contamination can cause acute losses.

• A new remineralisation recipe may change conductivity.
• Large cold water changes can shock recently moulted shrimp.
• Chloramine may be under-treated.
• Buckets, hands or sprays can introduce contaminants.

Timing is important: deaths during filling point toward acute exposure, while losses over several days may involve moulting, ammonia or a destabilised biofilter.

What to check first

• What were temperature, GH, KH, pH and TDS before and after?
• Was conditioner dosed for the full new-water volume?
• Did the source, bucket, hose or product change?
• Are fish and snails also affected?

Compare the result with the aquarium’s normal baseline, not only a generic target. Record the time, recent maintenance, new livestock, feeding changes, source-water details and any equipment fault. A short timeline often separates the original cause from secondary symptoms.

A practical action plan

1. 1. Stop the suspected sourceDo not continue adding water or products from the same preparation.
2. 2. Increase oxygen and test toxinsCheck ammonia, nitrite and disinfectant-treatment errors.
3. 3. Correct graduallyUse verified prepared water in smaller changes if dilution is required.
4. 4. Preserve evidenceKeep labels, source samples and the exact mixing record.

How to interpret the response

Survivors becoming active after stabilisation is encouraging, but delayed moulting problems can still occur. Continue observation through the next moult cycle.

Change one important variable at a time where welfare allows, then observe and retest. When several products or adjustments are made together, it becomes difficult to know what helped, what caused stress and whether the underlying problem remains.

What to avoid

Do not make repeated large changes with uncertain water, add extra minerals blindly, use copper-containing products or assume acclimation fixes chemical contamination.

When it is urgent

Mass immobility, twitching, escape behaviour, rapid deaths or a confirmed chemical exposure is an emergency requiring immediate dilution with safe matched water.

How to prevent it next time

Use dedicated equipment, condition and remineralise outside the tank, verify every new batch and keep source-water and TDS records.

Keep enough records to recognise the aquarium’s normal behaviour, water chemistry and equipment performance. Trends are more useful than isolated numbers, and early correction is usually safer than a large emergency change.