The tolerance of shrimp ponds is the maximum amount of shrimp that shrimp ponds can carry. Unit of calculation is kg shrimp / m2. This threshold depends on pond infrastructure (pond bottom, pond depth, depth), equipment investment (fans, air blowers), seed quality, technical level and management experience of the farmer …
According to studies, as late as the end of the season, waste (including shrimp feces, leftovers, dead algae) accumulate in the bottom of the pond, forming black sludge and decomposition of organic substances will create Toxic gas such as H2S causes dead shrimp. Waste is also a nutrient source for algae to thrive, when the algae decompose and decomposes, causing the oxygen demand in the pond to skyrocket.
The larger the shrimps, the higher the total weight of the shrimp, the pond becomes narrow. Poor environment makes shrimp weak, susceptible to infection, in many cases farmers have to harvest shrimp emergency. This will cause great damage to the farmers because it costs a lot of money to buy medicines before, plus the size of shrimps so the price is low.
According to Dr. Pornlerd Chanratchakool (Thailand) the tolerance threshold is as follows: In Thailand: 1.5 m deep pond, 36 horsepower / hectare (water fan), the threshold value of 1.8 – 2.5 kg shrimp m2 of pond (white shrimp); The pond is 1.2 m deep, 25 horsepower (hail), 1,3 kg (pond) – 1.5 kg (pond). and 0.6 – 0.8 kg shrimp / m2 pond (black tiger shrimp).
– Determine the amount of stocking in ponds: Farmers should not drop too thick with shrimps shrinkage is moderate but should actively drop stock density to avoid putting too much pressure on ponds.
– Determine the time of shrimp pond to the threshold: Compared with the value of the pond is 1.3 kg / m2, the shrimp is still developing well because it has not reached the threshold. Thus, before shrimp reaches the threshold, farmers should actively collect to create a favorable environment to help shrimp develop further or actively enhance the gas fan as well as control the density of algae appropriate (not too thick algae) .
Industrial ponds should have a depth of 2 – 2.5 m, ensuring the highest water retention of 1.6 – 1.8 m. Appropriate stocking density for intensive shrimp farming is 15 – 20 fish / m2, semi-intensive 8-14 fish / m2; White shrimp from 30 to 80 shrimp / m2. In addition, during the culture process, it is necessary to ensure that the fans are sufficient and that the farmers have a good technical knowledge and experience in stabilizing the pond environment parameters in the event of weather changes.
Also, please note, after long rain should check the pH in the pond. If the pH is low, use agricultural water-soluble lime with a dose of 10-20 kg / 1,000 m3; Maintain the water level in ponds from 1.3 to 1.8 m to avoid the variation of environmental factors. For algae phenomenon, farmers can apply microorganism fertilizer, to reduce toxic gas in the pond should use periodic bacteria.