01 · AquaGrow
What it is
Organisms and debris can collect on shrimp gills and shell. Heavy fouling interferes with breathing, particularly when oxygen is already low. Gill colour helps flag a problem, but cannot identify the organism or prove that an infection caused the damage.
Signs to watch for
- A fuzzy or dirty coating appears on gills, shell, or appendages.
- Gills become brownish or otherwise discoloured; colour alone is inconclusive.
- Shrimp feed less, move poorly, or gather where water is better oxygenated.
Common causes
- External ciliates, including Zoothamnium, Epistylis, and Vorticella, may attach to shrimp. Filamentous bacteria, algae, and trapped particles can produce a similar coating.
- Similar signs can have other causes: Fusarium infection or other causes of damaged, melanised gills. Sediment, chemical injury, or oxygen shortage without ciliate infestation.
How to confirm the cause
- A qualified aquatic animal health professional should arrange fresh gill and appendage wet mounts at an appropriate laboratory to identify attached organisms and assess fouling severity.
- Measure oxygen and review solids, feed waste, and bottom condition at the same time. Persistent lesions may need histology (microscope examination of tissue) or fungal/bacterial investigation; finding a ciliate does not explain every death.
What to do immediately
- 1
Check oxygen immediately when shrimp show breathing distress and restore adequate aeration.
- 2
Arrange professional examination and laboratory sampling while affected shrimp are still alive.
- 3
Review recent overfeeding, bloom changes, and sediment disturbance; correct identified causes gradually.
- 4
Use separate pond equipment and agree on a follow-up inspection to check whether breathing and feeding improve.
Prevention: your practical checklist
- Match feeding to tray observations and current shrimp biomass.
- Manage settled waste without stirring decomposing sludge through the pond.
- Maintain circulation and aeration, including vulnerable overnight periods.
- Manage inlet-water quality and sediment entry with suitable farm infrastructure.
- Inspect sampled shrimp routinely and keep pond-specific fouling records.
When to call an expert
- Call an aquatic animal health professional urgently if deaths rise, shrimp gather at the surface, or breathing becomes difficult. Check dissolved oxygen while arranging help.
- Arrange an assessment if these signs persist, feeding falls or growth stays behind the crop trend. Send water readings, recent input records and photographs; ask the laboratory how to collect samples.
Farmer questions
Will moulting solve the problem?
Shedding the shell can remove surface organisms, but persistent poor conditions permit fouling again. Weak shrimp may also moult poorly. Address the pond environment and the underlying illness.
Does a little fouling explain mortality?
Not necessarily. The organism, its abundance, gill damage, and oxygen conditions all matter. Ask the laboratory to interpret the finding alongside the mortality history rather than treating the microscope result alone.
What should I record before asking for help?
Note the pond ID, culture day, recent deaths, feed intake, water test readings and recent changes. Ask the laboratory about suitable samples before adding a treatment. A photograph alone cannot confirm the cause.
Sources & further reading
AI-assisted educational content and translations, source-checked 17 October 2026. Not an individual diagnosis or prescription. Independent aquaculture-health and native-language specialist approvals have not been supplied. Sources do not endorse AquaGrow.
- Some Forms of Gill Disease in Penaeid Shrimp ↗Proceedings of the World Mariculture Society; Lightner, 1975
- Diseases of Penaeid Shrimps in the Philippines — Ciliate Infestation ↗SEAFDEC Aquaculture Department, Aquaculture Extension Manual No. 16
- Disease Prevention and Health Management in Coastal Shrimp Culture ↗Food and Agriculture Organization of the United Nations, 1997
- Description of the Pathology of Gill and Skin Tiger Shrimp (Penaeus monodon) Attacked by Zoothamnium ↗Media Jurnal Ilmiah Perikanan & Kelautan; Gunanti Mahasri, 2008