Shellfish Breeding and Hatchery Management (2+1)

Procedure

Fabrication of biofilter and its components:

A biofilter can be fabricated in number of ways, based on availability of materials, its need and technical easiness. Following is description of a biofilter unit :

• A large sized plastic bucket (60-65l) can be used as the main holding container.
• An inverted plastic bucket at the bottom of tank to hold filtered water. A hole to be made in this bucket for inserting a P.V.C. pipe of diameter. Another hole is also made in the bucket through which an air pipe can be inserted, which serves the purpose of an air lifting system, as well as oxygenation.
• A PVC inlet pipe through which water from larval rearing tanks enters the biofilter. The end of this pipe in larval rearing tank is enclosed in a net to keep out larger particles which may clog the biofilter system.
• Before setting the biofilter unit all materials are washed with freshwater. The inverted bucket or basket provided at the bottom is provided with a fine velon screen to prevent the entry of any filtered material. It also serves the purpose of false bottom and watch collection unit.
• After setting up the false bottom, the tank is filled with gravel to a depth of about10 cm. Sand is then filled to a depth of 8 cm. Very small sized screen mesh maybe provided to check mixing of sand and gravel. Above the sand the 2^ndgravel layer and a 10 cm thick activated charcoal layer is provided above the gravel. Now the next, a gravel layer of thickness 10 cm and a sand layer of few inches thickness is provided above it.