Guide of Chitosan for Aquaculture Water Treatment

      Guide of Chitosan for Aquaculture Water Treatment 

Core demands of aquaculture water treatment: flocculate residual feed & feces, reduce water turbidity, inhibit algae growth, adsorb heavy metals, and cut ammonia & nitrite levels. Chitosan sourced from shrimp shells with medium-high degree of deacetylation (DDA) and low-to-medium viscosity is prioritized. Precise selection is categorized into three application scenarios.

I. Mandatory Core Technical Indicators (National Aquaculture Standard SC/T 3403-2018)

1. Degree of Deacetylation (DDA, the most critical parameter)

- First choice: DDA 90%~92% (gold standard for general aquaculture water purification)

It features high amino group density and sufficient cationic charge, delivering balanced performance in flocculation, adsorption and bacteriostasis. Compatible with both freshwater and seawater ponds, with moderate dissolving difficulty.

- For high-density intensive aquaculture / recirculating aquaculture systems (RAS): High-purity chitosan with DDA ≥95%

It boasts stronger chelating capacity for heavy metals and nitrites, suitable for shrimp/fish high-level tanks and indoor recirculating water facilities.

- ❌ Not recommended: DDA ＜85%

Insufficient amino groups lead to poor flocculation performance and weak solubility, drastically lowering water purification efficiency.

2. Viscosity (tested in 1% acetic acid solution at 20℃)

1. Conventional earthen ponds / large water surfaces: Low viscosity 50–200 mPa·s (main recommended grade)

Fast dissolution and uniform dispersion without forming viscous gel clumps; flocs settle at a moderate speed to avoid bottom hypoxia. Ideal for regular substrate conditioning, algae inhibition and turbidity reduction.

2. High-density high-level tanks / recirculating aquaculture systems: Medium viscosity 300–500 mPa·s

Longer molecular chains provide stronger bridging flocculation capacity. It forms larger, denser flocs for heavily polluted water rich in residual feed and algae, accelerating sedimentation.

3. ❌ Avoid high viscosity over 800 mPa·s

Prone to caking during dissolution; residual gel films wrap pond sediment, triggering severe bottom hypoxia and substrate deterioration.

3. Other Quality Control Benchmarks (Safety Thresholds for Aquaculture)

- Ash content ≤1.0%; premium grade ≤0.8%

High ash content equals excessive impurities, accumulating sludge on pond bottoms.

- Moisture ≤10%

- Heavy metals (Lead / Arsenic / Cadmium) ≤0.5ppm to prevent secondary water pollution

- Raw material: Shrimp shell chitosan outperforms crab shell chitosan with fewer impurities and higher ionic activity.

II. Chitosan Selection for Three Distinct Aquaculture Scenarios

Scenario 1: Conventional Earthen Ponds (Daily Water Purification for Fish, Shrimp & Crab)

Spec recommendation: DDA 90%, low viscosity 50–200 mPa·s, 80-mesh powder

- Functions: Flocculate residual feed and feces, lower water turbidity, suppress cyanobacteria & green algae outbreaks, mild chelation of heavy metals

- Application: Dissolve with acetic acid then spray evenly across the whole pond; dosage: 10–20 g per cubic meter of water

- Advantages: Cost-effective, easy dissolution, no hardening of pond sediment

Scenario 2: High-Density High-Level Tanks / Recirculating Aquaculture Systems (Heavily Polluted Water, Surplus Residual Feed, Excessive Nitrites)

Spec recommendation: DDA 92%~95%, medium viscosity 300–500 mPa·s

- Functions: Rapidly flocculate high-concentration organic matter, significantly reduce ammonia and nitrite, stabilize algae phases. Over 90% of suspended flocs can be trapped when matched with filtration equipment.

- Applicable to indoor recirculating farming systems for penaeid shrimp, grouper and sea bass.

Scenario 3: Emergency Algae Control, Red Tide / Cyanobacteria Outbreak Remediation

Spec recommendation: Low-molecular-weight chitosan oligosaccharide (degree of polymerization 2–20, DDA ≥90%)

- Advantages: Dissolves directly in cold water without acetic acid; penetrates algal cells to restrain reproduction, inhibits bacteria and improves anti-stress capacity of aquatic animals. Dual-purpose for feed mixing and water spraying.

- Limitation: Weak flocculation & sedimentation performance; only used as auxiliary additive, cannot fully replace standard chitosan for water purification.

III. Pitfall Guide: Unqualified Chitosan Products Widely Available on Market

1. Low-cost chitosan with DDA 70–80%: Poor solubility, white floc residues floating on water surface after application, ineffective for aquaculture water treatment.

2. High-viscosity chitosan customized for industrial wastewater: Easy caking when dissolved, consumes oxygen after sinking, easily causes floating death of fish and shrimp.

3. Waste-grade chitosan with high ash content: Rich in calcium carbonate and protein impurities, accelerating sludge buildup on pond bottoms.

4. Crude-processed crab shell chitosan: Higher risk of heavy metal residue compared with shrimp shell grades.

IV. Concise Purchasing Summary

1. Outdoor conventional earthen ponds: Shrimp shell chitosan, DDA 90%, low viscosity (best cost-performance)

2. High-density indoor recirculating aquaculture systems: Shrimp shell chitosan, DDA 92–95%, medium viscosity

3. Emergency algae suppression + feed addition for anti-stress: Use chitosan oligosaccharide in combination for synergistic effects

Yudacentury As a supplier of chitosan application solutions with 24years experience.

Our main products: chitin, chitosan, Hydroxypropyl Chitosan, Hydrochloride Chitosan, Chitosan Lactate, Carboxymethyl Chitosan.

With origin: Chitosan Fresh North Atlantic Shrimp Shell/Crab Shell Origin

Chitosan Aspergillus Niger Origin

Chitosan Agaricus bisporus Origin mushroom

More details and solutions ,please contact us.