How to Manage Fish Health for Better Farming Profits

Maintaining the health of your fish is the cornerstone of profitable aquaculture. Fish health management directly influences growth rates, feed conversion efficiency, and overall productivity in the pond. While fish farming may seem straightforward, neglecting proper health and water management can quickly undermine your efforts and lead to significant economic losses.

This guide provides a detailed overview of the practices and principles necessary for maintaining healthy fish, from pre-stocking pond preparation to post-stocking care, disease prevention, and treatment.

Understanding Pond Water Quality Management

Water quality is the most important factor in aquaculture. Proper pond management ensures that fish grow efficiently and resist diseases. Before stocking, ponds must be prepared carefully to provide a suitable environment for your fish. Two key practices in this regard are liming and fertilization.

1. Liming

Liming is the process of adding agricultural lime (calcium carbonate) to fish ponds to regulate pH levels. Lime raises the pH and buffers it against fluctuations, creating an environment conducive to fish health and growth. Liming also helps in controlling parasites in the pond by reducing harmful microorganisms, while promoting the decomposition of organic matter.

The amount of lime applied depends on the soil and water pH:

• Soil pH 4.5–5.0: Apply 2,000 kg/ha
• Soil pH 5.1–6.5: Apply 1,000 kg/ha
• Soil pH 6.6–7.5: Apply 500 kg/ha
• Soil pH 7.6–8.5: Apply 500 kg/ha
• Soil pH 8.6–9.5: No lime required

For general pond management, a baseline dose of 200–250 kg/ha of lime can be applied. Liming not only stabilizes pH but also improves soil structure and enhances the growth of natural plankton, a vital food source for fish.

2. Fertilization

Fertilization promotes the growth of natural food in ponds, such as plankton, which supports fish growth. Fertilization practices differ depending on the type of fish culture system: single-year culture (one-time stocking and final harvesting) or multiple stocking with partial harvesting.

Single-Year Culture Fertilization:

1. Basal fertilization: Apply cow dung at 2,000 kg/ha and lime according to soil pH.
2. 7 days after stocking: Apply 2/3 of the first month’s lime dose.
3. 8 days after stocking: Conduct bottom raking using a bamboo raker or rope-tied brick.
4. 15 days after stocking: Apply Single Superphosphate (SSP) at 16 kg/ha.
5. From the 2nd month onward: Repeat cow dung fertilization at 660–750 kg/ha, adjust lime as required, perform netting and bottom raking, apply urea at 20 kg/ha, and SSP at 16 kg/ha.

Multiple Stocking with Partial Harvesting:

Fertilization is done every 15 days as follows:

1. 7 days before stocking: Apply cow dung at 2,000 kg/ha (basal fertilization).
2. 3rd day: Apply cow dung at 500 kg/ha, SSP at 16 kg/ha, and urea at 10 kg/ha.
3. 10th day: Apply lime according to soil pH.
4. 11th day: Conduct bottom raking.
5. 18th day: Repeat the same fertilization as on the 3rd day.

Proper fertilization ensures a consistent supply of natural food for the fish while enhancing pond productivity.

Stocking the Fish Pond

Once the pond is prepared and fertilized, it is ready for stocking, usually 15 days after the initial fertilization. Correct stocking density and species proportion are essential to maintain fish health and maximize growth.

Stocking Density

• Permanent ponds: 5,000–10,000 fingerlings per hectare.
• Seasonal ponds: 2,000–3,000 fingerlings per hectare.

Species Proportion

• Surface feeders: 30–40% (e.g., Catla, Silver carp)
• Mid-water feeders: 30–35% (e.g., Rohu)
• Bottom feeders: 30–40% (e.g., Common carp, Mirgal)

Proper species composition ensures efficient utilization of different pond layers, reducing competition for food and promoting balanced growth.

Guidelines for Stocking Fish from Bags

Transporting fish in bags requires care to minimize stress:

1. Do not open bags until they reach the pond to preserve oxygen.
2. Place the bags in baskets or float them on the pond to adjust the temperature.
3. Gradually add pond water into the bag over 10–20 minutes to acclimate the fish to the new water conditions.
4. Allow fish to swim out naturally; avoid pouring them into the pond.

Note: Simply floating bags on the pond is insufficient. Proper acclimation is essential, especially for large grow-out pond stock.

Guidelines for Stocking from Transport Tanks

1. Position the tank as close to the pond as possible.
2. Check water quality in both the pond and the tank.
3. Remove one-third of the tank water and replace it with pond water.
4. Scoop out a few fish at a time into a bucket with water, then gently release them into the pond.

These procedures reduce stress and improve survival rates during stocking.

Post-Stocking Care

1. Supplementary Feeding

While natural food may suffice initially, supplementary feeding ensures faster growth and better survival:

• Feed mixture: Rice bran and groundnut or mustard oilcake in a 1:1 ratio.
• Feeding rate:
• Months 1–2: 3–4% of body weight
• Months 3–4: 2–3%
• Months 5–6: 2%
• After 6 months: 1%

Feed should be evenly distributed on bamboo trays or sprayed at pond corners.

Fish feed requirement formula

2. Netting and Harvesting

Trial netting serves to monitor fish growth and maintain water quality. Larger nets are used for periodic harvesting. Typically, fish reach table size within 9–10 months. Regular monitoring also helps prevent theft, which is common in rural aquaculture operations.

Fish Health Treatments

Proper treatment and prevention strategies are essential to minimize losses due to diseases.

Dip Treatment

• Fish are immersed in a concentrated chemical solution for less than a minute.
• Steps: Prepare solution → place fish in dip net → immerse fish → return to aerated pond water.

Bath Treatment

• Fish are exposed to a weaker chemical solution for longer durations: Short bath: A Few minutes to 1 hour
• Long bath: Up to 24–48 hours

Procedure: Mix the chemical evenly in water, immerse the fish for the required duration, then restore water levels gradually.

Conclusion

Maintaining fish health is critical for successful aquaculture. By implementing proper pond preparation, liming, fertilization, and stocking strategies, fish farmers can establish optimal growth conditions. Post-stocking care, including supplementary feeding, netting, and disease prevention, ensures healthy fish populations and maximizes productivity.

Additionally, understanding the symptoms of common bacterial and parasitic diseases, coupled with timely and appropriate treatment, allows farmers to mitigate losses effectively.

A well-managed, healthy fish population is the foundation of a thriving and profitable fish farm. By prioritizing water quality, proper nutrition, and disease prevention, fish farmers can achieve sustainable growth and long-term success in aquaculture.