In aquaculture, timely water replenishment and exchange are essential to maintain stable, healthy water quality. Fish and shrimp ponds often face challenges caused by feed residues, animal excretion, and decaying plankton. Without proper management, these factors lead to deteriorating water quality, stress, and even mass mortality.
The ultimate goal of water exchange is to keep pond water “fertile, fresh, clear, and lively,” ensuring an optimal environment for aquaculture species. Below are the main reasons why regular water replenishment and exchange are crucial.
Why Timely Water Exchange Matters
Boosting Dissolved Oxygen (DO)
High stocking density and organic matter decomposition consume large amounts of oxygen. By introducing fresh water (surface water or aerated well water), dissolved oxygen levels rise quickly, preventing oxygen depletion, fish surfacing, or sudden die-offs.
Diluting Harmful Substances
Toxic compounds easily accumulate in ponds and threaten aquatic life:
- Ammonia (NH₃-N): Derived from excretion and feed waste, highly toxic to fish and shrimp.
- Nitrite (NO₂⁻): A byproduct of ammonia conversion, it impairs oxygen transport in blood.
- Hydrogen Sulfide (H₂S): Produced under anaerobic conditions, extremely toxic and foul-smelling.
Water exchange effectively reduces these harmful concentrations and minimizes toxicity.
Regulating Temperature and pH
- Temperature Control: During hot summer, deep well water or cool water sources help lower pond temperature, reducing heat stress.
- pH Stabilization: Water exchange buffers daily pH fluctuations caused by algal photosynthesis or prolonged cloudy weather, keeping the environment stable.
Improving Algal and Microbial Balance
Adding new water introduces beneficial algae and microbes, which suppress harmful “black water” or “foul water.” This maintains a healthy algal community dominated by diatoms and green algae.
Meanwhile, partial exchange removes aging algae before they die, preventing toxin release and oxygen depletion.
Stimulating Growth and Metabolism
Flowing fresh water encourages fish and shrimp activity, boosts appetite, and promotes faster growth. Farmers often notice better feeding response after water exchange.
Practical Guidelines for Effective Water Exchange
Choose the Right Timing
- Sunny Days: Exchange water between 9–11 AM or 2–4 PM when DO levels are high.
- Avoid Bad Weather: Do not change water during sultry heat, thunderstorms, overcast days, or evenings, as it may trigger oxygen crashes and stress.
Monitor Water Quality and Color
- If water becomes too dark, red, white, or black (transparency < 20 cm), exchange water. Maintain 30–40 cm transparency.
- Regularly test key parameters:
- Ammonia > 0.5 mg/L
- Nitrite > 0.1 mg/L
- pH daily fluctuation > 0.5
- Replace 10–30% of pond volume per session. For heavily polluted ponds, increase gradually in multiple rounds to avoid shock.
Adjust by Farming Stage
- Nursery Stage: Focus on adding water to stabilize temperature and support natural feed development.
- Grow-Out Stage: As feeding increases, more frequent exchanges are required. During hot months, exchange water more often to control organic pollution.
Treat Incoming Water Before Use
- Sedimentation & Filtration: For river water, use settling ponds to remove predators, parasites, and suspended solids.
- Aeration: Underground or well water should be aerated to remove excess nitrogen/CO₂ and enrich oxygen.
- Disinfection: Suspected water sources should be treated with chlorine dioxide or bleaching powder, and residual chlorine neutralized before use.
Control Flow Rate and Temperature Difference
- Guide new water slowly into the pond along the wall or through buffers to avoid disturbing bottom sediments.
- Keep new vs. old water temperature within ±2℃. Fish fry and shrimp larvae are especially sensitive to sudden temperature shocks.
Manage Pond After Water Exchange
- Apply probiotics (e.g., Bacillus, EM bacteria) and fertilizers to quickly restore favorable pond color and microbial balance.
- Use zeolite or water conditioners to absorb toxins and stabilize pond quality.
Conclusion
In aquaculture, water exchange is not a simple operation but a core water quality management strategy. By following the principle of “Frequent, Small, and Stable,” farmers can reduce toxic buildup, stabilize water conditions, and create a thriving environment for fish and shrimp. This translates into higher survival rates, faster growth, and more profitable farming outcomes.
Recommended Equipment for Efficient Water Exchange
To achieve effective and safe water management, we recommend:
- Submersible Drainage Pump – Ideal for pond bottom water exchange, sludge discharge, and efficient drainage.
- Floating Drainage Pump – Designed for flexible surface water exchange and maintaining stable pond water quality.
These pumps are engineered for aquaculture applications, helping farmers achieve efficient, reliable, and cost-effective water exchange operations.
