01 · AquaGrow
What it is
Hydrogen sulphide (H2S) is a toxic gas that can form when organic waste breaks down without oxygen. A black bottom is a warning to investigate, not proof of H2S poisoning. It can also be dangerous to people.
Signs to watch for
- Black sludge or a heavily loaded pond bottom.
- Weak shrimp, poor feeding or unexplained deaths.
- A rotten-egg smell may occur, but absence of smell does not mean safety.
Common causes
- Uneaten feed, faeces and other organic matter accumulate.
- Poorly oxygenated sediment allows sulphide to form.
- Disturbing reduced sludge may expose shrimp to poor-quality bottom water.
How to confirm the cause
- Have a technician assess water and bottom conditions, including sulphide testing with an appropriate method.
- Measure DO and pH. Do not deliberately sniff sludge or enter a sludge pit or enclosed tank.
What to do immediately
- 1
Keep people out of sludge pits and enclosed tanks. Move away and seek emergency medical help if gas exposure causes dizziness or breathing trouble; do not attempt an unprotected rescue.
- 2
Maintain safe aeration without churning black sludge into the pond. Pause feeding if shrimp are distressed.
- 3
Call a qualified aquaculture technician for sulphide, DO and pH checks and a pond-specific recovery plan.
- 4
Do not drag the bottom or apply acids, oxidisers or a product mix as an emergency experiment. Use controlled waste or water removal only under technical direction.
Prevention: your practical checklist
- Match feed to consumption and remove waste through a planned, safe system.
- Prepare and manage the pond bottom between crops.
- Monitor bottom condition and circulation; investigate recurring black zones.
When to call an expert
- Seek urgent help for deaths or breathing stress near black-bottom areas or after sludge disturbance.
- Any suspected worker gas exposure is a human emergency, separate from the pond treatment plan.
Farmer questions
Can I diagnose H2S by smell?
No. Smell is not a safe test; the ability to smell the gas can be lost. Use appropriate testing and keep people away from suspected gas hazards.
Is every black pond bottom H2S poisoning?
No. Black sediment signals poor bottom conditions, but the cause of shrimp illness needs water tests and a wider assessment.
Should I stir the bottom to release gas?
Do not stir reduced black sludge into a stocked pond. Ask a technician for a safe bottom-management plan.
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.
- Shrimp culture and disease management training manual (2022) ↗ICAR-CIBA
- Soil and water quality management — Technical Advisory Series No. 7 ↗ICAR-CIBA
- Hydrogen sulfide: worker health hazards ↗OSHA (worker safety, not shrimp treatment)