Shrimp deaths after a water change: what to check

Deaths after a water change call for investigation of both the replacement water and the other maintenance. The timing does not establish that the change itself, copper or pH caused the loss. Stop any ongoing suspicious addition, check filter operation and improve surface movement if needed. Do not wait until tomorrow when several animals are in distress.

Record what changed

1. Record the volume removed and added, the water source, preparation and refill speed. Keep product names and doses.
2. Measure temperature, pH, ammonia and nitrite. Where possible, compare GH, KH and conductivity between tank water and the actual replacement water. One TDS reading cannot identify contamination.
3. Check whether the filter, substrate or plants were cleaned at the same time. A stopped filter, disturbed debris or remaining dead animals may create an additional problem.
4. Check the bucket, hose, products and recently added plants or decor. Use equipment free from soap or cleaning residues.

Do not repeat the exposure with the same suspect water

With likely contamination or detected ammonia/nitrite, suitable prepared clean water may be needed to reduce exposure. The amount and repetition depend on readings, the animals and replacement-water quality. A fixed small maximum can be inadequate after a large exposure. Equally, repeating a change from the same unknown source without investigating it may not help.

For tap water, check whether the utility uses chlorine or chloramine. Treat any disinfectant present with a suitable product according to its label. Standing alone does not reliably remove chloramine. Conditioner does not correct unsuitable hardness or prove that every contaminant has disappeared.

Remove visible dead animals and leftover food and pause supplementary feeding. Keep biological filter media operating; do not replace or clean everything at once. Retest after mixing. Continued deaths or loss of balance warrant help from an aquatic animal-health professional, using your readings and timeline.

Plan the next maintenance session

Prepare water outside the tank, use a thermometer and check the appropriate mineral composition. Track what was actually removed: evaporation leaves minerals behind, while siphoning removes them. Avoid combining a major rearrangement, new water source and filter replacement without a specific need.

Neocaridina, bee/Taiwan Bee, Cardinal and fan shrimp do not share one suitable water recipe. Use the water decision guide for your setup. Do not force pH back simply because you suspect pH shock. Fish appearing normal do not establish that the water is safe for shrimp.

Sources and scope

• CDC: Chlorine and chloramine in drinking water
• UF/IFAS: Ammonia in Aquatic Systems
• US EPA: Dissolved oxygen
• US EPA: Aquatic life criteria for copper

The sources explain disinfectants, nitrogen chemistry, oxygen and copper risk. The investigation sequence is our editorial judgement. Timing alone does not establish a diagnosis or a universal water-change percentage.