Quick answer: For routine aquaculture pond disinfection, dose 0.5–1.0 ppm Sodium Dichloroisocyanurate (SDIC) 60% as a preventive measure every 7–10 days. For pre-stocking pond sterilization, use 30–50 ppm SDIC with 48-hour retention before introducing aquatic species. During disease outbreaks (white spot, vibriosis), shock-dose at 5–10 ppm SDIC. Always test pH (target 7.5–8.5) and ensure proper aeration before and after dosing.
Sodium Dichloroisocyanurate (SDIC) is the most widely used chlorine donor in modern aquaculture because of its neutral pH after dissolution, broad-spectrum biocidal action, and rapid degradation that leaves no harmful residue. This guide compiles the dosing practices used by Shilan Chemical‘s technical team across shrimp, fish, and crustacean farms in Southeast Asia, Latin America, and Africa.
Why SDIC Outperforms Other Chemical Choices in Aquaculture
Aquaculture operators have three primary chlorine choices: calcium hypochlorite, sodium hypochlorite (liquid bleach), and SDIC. SDIC dominates modern best practice because:
- Neutral pH dissolution (6.0–7.0): Does not shock the pond’s existing alkalinity buffer, preserving the microbial balance critical for healthy growth
- Stable solid form: Easy to ship, store on-farm, and dose precisely — no leaks, no concentration loss over storage time
- 56–60% available chlorine: Significantly higher than calcium hypochlorite (65–70% in theory, but unstable in practice), with predictable release rates
- Zero residual heavy metals: Unlike calcium hypochlorite which leaves calcium scale and trace heavy metals, SDIC fully degrades into harmless components
- Compliance friendly: Approved for aquaculture use under FAO, FDA, and EU EFSA guidelines when applied within recommended limits
Core SDIC Dosing Formula for Aquaculture Ponds
SDIC Required (kg) = Pond Volume (m³) × Target Chlorine (ppm) ÷ Active Chlorine % ÷ 1,000
Example Calculation
For a 1,000 m³ shrimp pond requiring 1 ppm preventive treatment with SDIC 60%:
1,000 × 1 ÷ 60 × 100 ÷ 1,000 = 1.67 kg of SDIC 60%
Ready-to-Use Dosing Tables
Routine Preventive Treatment (Every 7–10 Days)
| Pond Size | SDIC 56% (kg) | SDIC 60% (kg) | Target Free Chlorine |
|---|---|---|---|
| 500 m³ | 0.9 | 0.83 | 1.0 ppm |
| 1,000 m³ | 1.8 | 1.67 | 1.0 ppm |
| 5,000 m³ | 8.9 | 8.33 | 1.0 ppm |
| 10,000 m³ | 17.9 | 16.7 | 1.0 ppm |
Pre-Stocking Pond Sterilization (Empty Pond, 48-hour Retention)
| Pond Size | SDIC 60% Dose | Wait Time Before Stocking |
|---|---|---|
| 500 m³ | 25 kg | 48 hours min, 72 hours preferred |
| 1,000 m³ | 50 kg | 48 hours min, 72 hours preferred |
| 5,000 m³ | 250 kg | 48 hours min, 72 hours preferred |
Emergency Outbreak Response (Stocked Pond — Use With Caution)
| Pond Size | SDIC 60% Shock Dose | Critical Precautions |
|---|---|---|
| 500 m³ | 4.2 kg (5 ppm) | Continuous heavy aeration, harvest within 14 days if dose exceeds 8 ppm |
| 1,000 m³ | 8.3 kg (5 ppm) | Same as above |
| 5,000 m³ | 41.7 kg (5 ppm) | Same; consider partial water exchange before dosing |
Application Procedure: 7 Steps for Maximum Safety
- Measure pond volume accurately using surface area × average depth. Errors of ±20% are common and dangerous
- Test water parameters first: pH, dissolved oxygen, ammonia, temperature
- Pre-dissolve SDIC in a separate container with 20× volume of pond water; stir for 2 minutes
- Apply during cooler hours (early morning or late evening) to avoid stressing stocked species
- Distribute evenly across pond surface using a boat or shore-based broadcast for ponds >500 m²
- Run aerators continuously for at least 6 hours after dosing
- Re-test free chlorine after 30 min to confirm target ppm reached
Common Dosing Mistakes That Kill Shrimp
Mistake 1: Over-dosing in Hot Weather
Higher water temperature accelerates chlorine reaction, meaning the same dose delivers higher peak chlorine. Reduce dose by 20% when water exceeds 30°C.
Mistake 2: Skipping Aeration
SDIC consumes dissolved oxygen during disinfection. Without continuous aeration, oxygen drops below 3 ppm within hours, suffocating stocked species.
Mistake 3: Dosing During Algae Bloom Crashes
Decaying algae already strip oxygen. Adding SDIC accelerates the crash. Always do partial water exchange first.
Mistake 4: Mixing SDIC With Other Treatments
Never combine SDIC with formalin, potassium permanganate, or ammonia-based products. Wait 48 hours between treatments.
Pond-Type Specific Recommendations
For Shrimp Ponds (Pacific White Shrimp, Black Tiger)
Pre-stocking: 30–50 ppm SDIC, 72-hour retention before PL stocking. Grow-out cycle: 0.5–1.0 ppm weekly with PCR-based vibrio screening.
For Tilapia and Carp Fingerling Ponds
Pre-stocking: 20–30 ppm SDIC. During grow-out: 0.3–0.5 ppm bi-weekly. Tilapia is moderately chlorine-sensitive — never exceed 1 ppm in stocked ponds.
For Prawn (Macrobrachium) Hatcheries
SDIC 60% effervescent tablets at 0.2 ppm in larval tanks. Critical: aerate continuously and maintain pH 7.8–8.2.
FAQ
Can I use SDIC daily in stocked aquaculture ponds?
No. Daily dosing eliminates beneficial nitrifying bacteria. Use SDIC only weekly for prevention or for emergency outbreak response.
How long does SDIC stay active in pond water?
In tropical conditions (28–32°C), free chlorine from SDIC degrades to safe levels within 6–12 hours. In cooler temperate water, residual chlorine may persist up to 24 hours.
Will SDIC harm beneficial probiotic bacteria I’ve added?
Yes, SDIC kills both pathogens and probiotics. Re-inoculate beneficial bacteria 48 hours after SDIC treatment, once free chlorine drops below 0.1 ppm.
What is the harvest withdrawal period after SDIC treatment?
For routine 1 ppm preventive dosing, no withdrawal is required because residue is undetectable within 24 hours. For shock doses above 5 ppm, observe a 14-day withdrawal before harvest.
Sourcing Aquaculture-Grade SDIC
Shilan Chemical supplies Veterinary GMP-certified SDIC 60% specifically formulated for aquaculture use, with batch-specific COA confirming heavy metal levels below FDA limits. We export to shrimp farms across Vietnam, Ecuador, India, Indonesia, and Bangladesh. Contact our aquaculture specialist team for bulk pricing or sample requests.