A Detailed Guide to the Latest Scientific Tilapia Farming Techniques

I. Pond Conditions and Production Facilities

The experimental pond has an area of 10 mu, a water depth of 2.5 m, a water source of river water, a clay bottom, and about 15 cm of silt. It is equipped with an independent water inlet and drainage system, as well as 1 generator unit of 15 kilowatts, 1 small pellet feed machine, 2 paddlewheel aerators of 1.5 kilowatts, and 1 impeller aerator of 3 kilowatts.

II. Fingerling Stocking

Before stocking, clearing and disinfection were carried out according to conventional farming methods, and rational polyculture was adopted under a high-yield, high-efficiency farming model. From April 15 to 18, 2007, a total of 12,000 GIFT strain Genomar tilapia (size 40 fish/kg), 3,000 freshwater pomfret (size 20 fish/kg), 500 bighead carp (size 4 fish/kg), 800 silver carp (size 4 fish/kg), and 500 Pengze crucian carp (size 40 fish/kg) were stocked. All fish entering the pond were given a medicated bath in potassium permanganate in sealed cages and then directly stocked into the pond.

III. Feed Management

Based on the feeding habit of freshwater pomfret, which can directly consume soybeans, the feeding time was staggered from that of tilapia. Feed was given twice daily, in the morning and afternoon. Soybeans were weighed out at 3%-6% of the total body weight of freshwater pomfret (flexibly adjusted according to each stage of farming), soaked for 4 hours, and then fed first at fixed points. After 1 hour, pelleted feed was fed at fixed points at 0.5%-5% of the total body weight of tilapia.

Water temperature 20-22°C, body weight 30-100 g, feeding rate 3-5%; water temperature 22-25°C, body weight 100-300 g, feeding rate 3-4%; water temperature 25-28°C, body weight 300-500 g, feeding rate 2-3%; water temperature 28-30°C, body weight 500-800 g, feeding rate 1-2%; water temperature 30-32°C, body weight 800-1000 g, feeding rate 0.5-1%.

In order to save costs and take into account the physique and growth rate of the main cultured fish, a small feed machine was used to adjust the feed formula at each stage, which can greatly reduce farming costs, increase growth rate, and enhance the fish body's own disease resistance. The specific practice is: while adjusting the formula, regularly add microbial preparations and disease-prevention drugs. Generally, within one month, medicated feed containing disease-prevention drugs is fed for 5-7 days, and microbial preparations are added throughout the rest of the time. Although microbial preparations suffer some loss under high heat, through farming observation and comparison, they were higher than other ponds under the same conditions without added microbial preparations in all aspects such as enhancing physique, disease resistance, and increasing growth rate. The feed formulas for each stage are shown in the table.

IV. Water Quality Management

Properly adjusting water quality can promote normal fish growth, effectively prevent disease occurrence, and increase farming yield.

1. Maintain a relatively high water level to effectively utilize the growth of fish in various water layers. In particular, the water level of polyculture ponds should be kept relatively stable at about 2.5 m. In summer high-temperature seasons, change the water once a week or every 10 days, drain the bottom-layer sewage, add fresh water, with a water exchange volume of about 1/5, draining and filling at the same time to keep the water level stable.

2. Regulation and control of physical and chemical factors in the water environment

(1) The level of dissolved oxygen is an important factor determining fish growth. Keeping pond water dissolved oxygen above 5.0 mg/L throughout the day is most beneficial to the growth of various fish, enhances fish appetite, and can convert harmful substances in water into harmless substances. The specific practice is to turn on the aerator at appropriate times so that the pond water forms a circulating state. When the stock density in the pond is relatively high, the aerator must be turned on for 2-3 hours at noon to release harmful gases in the water, dissolve fresh oxygen, promote the growth of other aquatic organisms, and benefit the growth of filter-feeding fish.

(2) The pH level also affects the growth of fish and other organisms. Properly adjusting the pH can prevent disease and promote growth. Generally, quicklime is broadcast once every half month, with an amount of 15-20 kg per mu at 1 m water depth, so that the pond water pH remains stable between 6.5 and 8.5.

(3) In fish ponds using complete formula feed, after 2-3 months of farming accumulation, ammonia nitrogen and nitrite in the pond are generally relatively high, affecting fish growth and very easily causing fish poisoning, disease, or even death. Effective measures should be taken to regulate and control this. By turning on the aerator more often, applying special oxygen-increasing and water-improving agents, bottom substrate improvers, or sprinkling zeolite powder (20-30 kg per mu), ammonia nitrogen and nitrite in the water body can be reduced, promoting the reproduction and growth of beneficial organisms.

(4) Regularly use microbial preparations such as EM bacteria and biological water-protecting agents (Bacillus subtilis, Rhodopseudomonas palustris, sulfur bacteria, nitrifying bacteria, denitrifying bacteria, etc.), which can inhibit the reproduction of harmful algae and harmful microorganisms, promote the growth of beneficial algae such as green algae and diatoms, purify water quality, and enhance the immunity of aquatic organisms. Generally, when the water temperature is 20-32°C, dilute and activate with water, then evenly splash over the whole pond on a sunny morning. Do not change water within 5-7 days after use, and do not splash disinfectants within 5-7 days before use, so as not to affect the effectiveness of the microbial preparations.

V. Fish Disease Prevention and Control

Throughout the experimental farming process, the policy of “prevention is more important than treatment” was implemented. Drug prevention was carried out before the seasons when fish diseases occur frequently, feeding areas were regularly disinfected, and water quality regulation was combined with medicated feed prevention. A total of two disease outbreaks occurred during the farming process.

1. The first occurred in July when adult pomfret were harvested for market. Some tilapia were injured, and due to high density, skin ulceration infection with Aeromonas hydrophila occurred. The body surface of diseased fish showed patchy ulceration, body surface congestion, scale loss, exposed muscle, and red patch-like lesions. Prevention and treatment: sprinkle strong chlorine powder over the whole pond to make the pond water concentration 0.3 g/cubic meter, with a 3-day course of treatment, and at the same time feed Xinlikang medicated feed for 6 days. The condition improved.

2. The second occurred in mid-September and was caused by Streptococcus infection. The diseased fish had darkened body color, protruding eyeballs or cloudy white and bleeding eyes, punctate congestion on the abdomen, congestion inside the gill cover, ascites in the abdominal cavity, and redness around the anus. Prevention and treatment: splash chlorine dioxide over the whole pond at 0.3-0.5 g/cubic meter for disinfection, once every other day; at the same time feed allicin medicated feed for 5 days.