Why are my shrimp dying? Investigating the causes

“My shrimp are dying” alone does not identify a reliable cause. Build a timeline of losses, measurements and changes, and test possible explanations separately. During active severe deterioration, use the emergency plan first; investigation and support may be needed together.

Record the order of events

Start with the last period without known problems. Record numbers, first abnormal behaviour and confirmed carcasses. Add purchases, feeding, water changes, filter work, equipment failures and products, including dates and times. Write “unknown” for missing information rather than turning a plausible memory into a measurement.

• Which species or line is affected? Are other inhabitants, new purchases and established animals affected similarly?
• Are cases sudden and numerous or spread over time? Is the carcass count an actual count or an estimate of missing animals?
• What was measured before and during the problem? Keep units, test names and source-water results. A later normal test cannot exclude an earlier temporary abnormality.
• Which action preceded improvement or deterioration? Record simultaneous interventions so their effects are not incorrectly attributed separately.

From timing to a testable explanation

Losses after a water change indicate a need to compare source water, preparation and equipment; they do not prove TDS shock. Problems after a plant purchase make origin relevant but do not prove pesticide exposure. White growth can justify targeted examination without identifying an organism from a photograph.

For each possibility, use the same record: observation, possible explanation, missing information, next check. For a stopped filter, for example, check flow and nitrogen readings. For a new lesion, document growth and behaviour and seek identification. Do not invent a probability without data.

Several problems can coexist

Water problems, injury and disease are not mutually exclusive. One Neocaridina investigation described bacterial, fungal-like and algal findings in the same outbreak. During serious or continuing losses, do not delay clinical help until every possible water problem is excluded.

A series of measurements helps describe the course, but one severe abnormal result can already require action. Normal readings while deaths continue do not resolve the case. Keep the record for a veterinarian familiar with aquatic animals; ask how samples should be supplied before collecting them. Continue recording new losses and keep suspect groups and equipment separate.

Sources and scope

• Merck Veterinary Manual: Management of Aquarium Fish
• UF/IFAS: Ammonia in Aquatic Systems
• UF/IFAS: Fish Health Management Considerations in Recirculating Aquaculture Systems
• Bauer et al. (2021): Cladogonium in a multifactorial disease outbreak

The clinical source largely concerns fish; we use history gathering, not its treatment protocols. The Neocaridina study describes multiple findings in one outbreak. This is our method for separating hypotheses from evidence, not a ranking of cause frequencies.