The trend of eating fish meat is slowly starting to increase in Indonesia. Fish meat is becoming popular because it contains good nutrition for the body. One of the most popular consumption fish commodities is tilapia. Tilapia is very popular in Indonesia, besides having a delicious meat taste, tilapia has a fairly high nutritional value compared to other fish at a more economical price. Therefore, the demand for meat is also getting higher. To overcome this, a technology is needed to increase production. Among cultivators, tilapia is favored because of its fast growth rate, strong immune system, efficient feed, and adaptability to various cultivation environmental conditions. One of the containers or media that is often used in conventional tilapia cultivation is to use an ground pond. The use of ground ponds for fish farming activities is very common for the people of Indonesia. Among the commodities that are commonly kept in earthen ponds are catfish, goldfish, carp, and so on. To obtain maximum results in tilapia cultivation in ground ponds, there are several things that need to be considered. According to (Hasan, et al., 2020) before cultivating tilapia in ground ponds, soil and water management should be carried out. This is done so that the condition of the pond is adequate for the maintenance of tilapia. Management of soil ponds includes removal of mud (if previously the pond has been used for fish rearing), drying, eradicating pests, liming and fertilizing.
The purpose of the management of the ground pond is to break the cycle of pathogenic bacteria, increase oxygen levels which help aerobic bacteria in decomposing and reforming organic matter, the loss of toxins from feed residues and previous rearing manure, and the pond ground will be oxidized by oxygen from the air. The following are the details of soil management in ground ponds for tilapia rearing:
1. Pond drying
Pond draining should be done before starting fish rearing in ground ponds. This aims to break the cycle of pathogenic bacteria produced from the previous cultivation process. Pond drying is carried out for 7-14 days or until the pond ground becomes dry which is indicated by the presence of cracks in the ground, looks bright in color, and has no odor. Care needs to be taken so that the ground is not too dry (20% water content), because it will interfere with the natural food that lives at the bottom of the ground pond.
Liming aims to increase ground pH, increase nitrate levels, maintain environmental sanitation of aquaculture ponds, stimulate microbes in the decomposition process of organic matter (Jubaedah, Sasanti, Marsi, & Mukhlas, 2020). Liming is done after 7 days of drying or the bottom ground of the pond has been dried. Before liming, before doing the type of ground at the bottom of the pond and testing the level (pH) of the soil using a pH ground tester or pH fox. The pH value required for fish rearing is 6 or neutral. The type of lime used varies depending on the willingness and ability of the cultivator. The dose is adjusted to the type of pond bottom soil and the desired pH value. Liming is done by spreading it on the soil surface of the pond bottom. For example, the use of quicklime (CaO) on grounds with a pH of less than 4 to raise the pH to 6 is 500-1 ton/ha. The more clay the bottom of the pond, the more lime is used. And if the dominant ground type is sandy ground, the dose of lime can be reduced.
Fertilizer is given with the aim of increasing the concentration of inorganic nutrients, increasing the number of phytoplankton, zooplankton, and finally increasing fish production. carried out 3 days after the liming process. The fertilizers given can be in the form of organic or inorganic fertilizers, such as manure for organic fertilizers or urea for inorganic fertilizers (Chairil, Hasan, & Prasetio, 2020). Provision of manure as basic fertilizer is given as much as 100-500 grams/m2 depending on the fertility level of the pond. While the provision of inorganic fertilizers (urea/TSP) can be given as much as 10 grams/m2. After that the pond is left for 7-10 days, then filled with water.
4. Water filling
Filling of water in the pond is done regularly. This is so that phytoplankton can grow first before adding fish seeds. In the early stages, after the fertilization process. The pond is filled with water up to 10-15 cm. Then let stand for 2-3 days until the pond water is greenish as a sign that natural food has grown. Then the pond water is added back according to the depth of the pond.
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