Why are my shrimp dying? The usual causes, ranked

If shrimp are dying right now, the cause is usually on a short list, and the items on it are not equally likely. Roughly in order of how often they turn out to be responsible: an un-cycled or recently disturbed filter, a swing in TDS or GH, copper or another invertebrate toxin, untreated tap water, temperature shock, pesticide residue on new plants, overfeeding, and moult failure. That ordering reflects hobby experience, not a published survey. Moult failure sits last because it is usually a downstream symptom rather than a cause. Check the rate first: Neocaridina davidi are commonly cited as living roughly 1 to 2 years, so an occasional body in a colony of 100 is normal. Five deaths in a day is an emergency; two in a week in a breeding colony is not.

Triage: the first hour

1. Stop feeding. Remove uneaten food and any bodies.
2. Test, and write the numbers down. Ammonia, nitrite, nitrate, pH, GH, KH, TDS and temperature (GH is mineral hardness, KH carbonate hardness, TDS total dissolved solids). Use a liquid kit for ammonia and nitrite, not strips.
3. Test your change water separately, straight out of the bucket. A fair number of die-offs trace back to the water going in.
4. List what changed in the last seven days. Plants, decor, a filter clean, a fertiliser dose, a medication, second-hand gear, an aerosol sprayed in the room, hand soap or sunscreen on your hands, or CO2 left on all night.
5. Only then decide on a water change. If ammonia or nitrite reads above 0 mg/L, or you suspect a toxin, change water that is temperature- and TDS-matched, added slowly. If everything tests clean, resist a big change just to be safe: a panic 50% change with mismatched water commonly causes the second wave.

The usual causes, ranked

1. The tank is not cycled

Ammonia and nitrite should both read 0 mg/L. Ammonia is generally the more acutely toxic, but nitrite is the one keepers miss, since it climbs after ammonia has come back down. Suspect it in any tank under about 8 weeks old, or a day or two after a filter clean or substrate vacuum. Rinsing media under the tap exposes the nitrifying bacteria (the helpful waste-processors) to chlorine and can knock out much of the colony. Fix it with small daily matched changes and seeded media (filter material from an established tank), no food and no new stock, and work through how to cycle a tank for shrimp before you restock.

2. Parameter swings, especially TDS and GH

In established tanks this is the cause that comes up most often, though there is no good data on the true split. A 40% change using water at around 50 ppm drops a 200 ppm tank to roughly 140 ppm in ten minutes, and that delta is harder on them than sitting permanently at 240 ppm. Keep changes to 10 to 20% weekly, match temperature within about 1 °C and TDS within 20 ppm, and add water slowly. Volume itself is disputed: plenty of experienced keepers run 50% weekly without loss, arguing the risk is the delta, not the litres. Neocaridina want 6-10 dGH, 2-6 dKH, 150-250 ppm TDS and a pH held steady between 6.8 and 7.8, with the reasoning and the testing routine in our Neocaridina water parameters guide, while the softer, more acidic Caridina figures are set out in water parameters for Caridina and Taiwan Bee shrimp. Our Neocaridina are raised in remineralised Melbourne tap water with an input TDS of around 60, dosed to about 160 TDS, so aiming near that eases the transition.

3. Copper and other invertebrate toxins

Fast and whole-tank: shrimp swimming erratically then dropping, snails sealed up, fish fine. Copper affects shrimp at concentrations most fish tolerate easily. Sources include some fish medications, particularly ich and parasite treatments, snail-killing products, algaecides, heavily dosed fertilisers, brass fittings and copper plumbing. Non-copper culprits behave the same way: aerosol spray in the room, which an air pump pulls straight in, plus hand soap, sunscreen and flea treatment on your hands. There is no quick antidote: move the shrimp to known-safe water if you have any, run a copper-specific chelating resin (a filter medium that chemically locks copper away), and do repeated matched changes. Plain activated carbon is not a reliable copper remover. Published safe limits for freshwater invertebrates vary widely; the hobby figure is under about 0.01 mg/L.

4. Untreated tap water

Chlorine gasses off if water stands and is aerated. Chloramine does not. Some Australian supplies are chloraminated rather than chlorinated, varying by area and season, so check your water retailer's report rather than assuming. Use a conditioner that states it handles chloramine, and dose for the full volume of new water in the bucket.

5. Temperature shock

Neocaridina are commonly kept between 18 and 28 °C with 20 to 24 °C as the target, and a swing of several degrees overnight is harder on them than a steady cool figure, so check with an independent thermometer rather than the heater dial. Unheated tanks and cold snaps are covered in keeping shrimp through an Australian winter, and animals that have been sitting cold in transit need the slow, temperature-first float and drip set out in our Shrimp Care and Acclimation Guide.

6. Pesticide-treated plants

New plants can trigger a die-off 2 to 10 days after they go in, because stock grown emersed (above water) for the nursery trade may carry systemic insecticide (pesticide absorbed into the plant's own tissue) that rinsing will not remove. Quarantine new plants in a shrimp-free tank for three to four weeks, longer if you can, or start with tissue-culture plants, which are the safer option since they are grown in sealed sterile media; best plants for a shrimp tank covers which species are worth the wait.

7. Overfeeding

Shrimp graze biofilm (the thin film of microbes on every wet surface) constantly, so what you add is a supplement: offer an amount they clear in 2 to 3 hours, remove the leftovers, and see feeding shrimp: what, how much, how often for amounts and frequency. Surplus food also feeds hydra and planaria, and whether planaria take healthy shrimp or only scavenge weak and moulting animals is genuinely disputed, so read planaria, hydra and scutariella if a colony never grows.

8. Moult failure

A white band at the join between carapace (the head-and-back shell) and abdomen, on a shrimp that is stuck or twitching, is what the hobby calls the white ring of death, and it is usually downstream of a GH or TDS swing rather than a cause in its own right. Juveniles moult more often than adults, so hold parameters steady for the first fortnight after our unsexed 0.8 to 1.2 cm juveniles arrive, and work through shrimp moulting problems and the white ring of death for what to change.

Usually not the cause

• The grade. Grading runs Entry, Mid, High and Collector and describes appearance only. It is explicitly not a health rating.
• Snails. Common tank snails compete for food rather than kill shrimp; snails dying alongside your shrimp points at copper.
• pH itself, within reason. A stable 7.6 suits Neocaridina fine. A pH that moves 0.6 in a day does not.

If they died on arrival

That is a transport question. We ship livestock on Mondays and Tuesdays; claim within 8 hours of delivery with photos and a short video of the animals in the unopened bag, and the remedy is replacement or refund of the livestock value, your choice. The detail is in the DOA and Missing Items Policy. Losses that begin on day three or four are more often tank-side, although delayed transport stress can contribute, so write your numbers down before you ask: "GH 3, TDS 110, nitrite 0.25 mg/L, three days after a 50% change" comes close to answering itself.