Through a circulating filtration system, Mr. Le Duc Canh, from Thanh Tri district, Hanoi, raises sea crabs indoors on a large scale.
The model of indoor sea crab farming is not new in the world but has just started appearing in Vietnam in 2019.
About 5 months ago, Mr. Le Duc Canh, 37 years old, residing in Van Phuc commune, Thanh Tri district, brought this model to apply for the first time in Hanoi. This is also the second indoor crab farm in the North, next to another in Ha Long, Quang Ninh province.
To save space, sea crabs are raised in small plastic boxes, arranged in trusses and numbered. Normally, each cell will only raise one animal to avoid eating each other.
With 1,000 boxes of crabs, Mr. Canh used to rent a car to transport about 30 blocks of seawater from Ha Long to Hanoi and initially invested about 450 million VND. “The water will be changed once a year. The amount of evaporated water will be added with fresh water combined with artificial sea salt”, Mr. Canh shared.
Two varieties of farmed crabs are nuggets and shell crabs. In, the shelled crab has high nutritional value and is harvested as soon as the shell is finished.
Currently, in the market, soft-shell crabs are quite scarce due to the difficulty of catching and even extensive farming. The price per kg can be up to 800,000 VND.
At the time of buying the seed, the crabs were all large with about 6 fish/kg. After about 20-45 days of rearing in boxes, crabs start to harvest, then reach about 4 fish/kg. Choosing large crabs to raise instead of small crabs is to shorten time and costs.
The crabs were mainly fed fish and snails, twice a day. The quality of crab meat currently does not depend on their movement space but on the nutritional composition of the food.
The heart of this model lies in the circulating water filtration system, which creates oxygen gas. Leftover food and waste of crabs will go through the coarse filter system, then to the microbiological tank and the bacteria removal system by UV light.
Microorganisms that cling to and live in kindness (acting like corals) will eat crab waste and leftover food suspended in the water to help make the environment cleaner. “The filter runs continuously day and night, usually every 4 hours, the machine will rest for about 15 minutes,” Mr. Canh said.
Sea crab farming water is regularly tested, at least 3 times a day to check the pH and salinity. Mr. Canh said that the first time the crabs died quite a lot because they could not control the water source.
Currently, Mr. Canh’s crab farm has started retailing to local customers.
According to Mr. Canh, indoor crab farming has the advantage of being unaffected by the weather, taking care of less labor, and shortening the farming time by about 2 months compared to extensive farming. However, to really bring economic efficiency, each farm needs to raise 5,000 boxes or more. “Then I can take advantage of the filtration system, helping to reduce operating costs,” Mr. Canh said.