Water Management

Round tank super intensive shrimp farms require a lot of water renovation. This is because the standing biomass of shrimp per m3 is very high (in the 2-3-4 kilos per m3 range). Water exchange is used to hydraulically remove wastes, settled floc, molts, uneaten feed and mortalities from the tank bottom.

Farm Design - Water flow between reservoirs - Generally, the raw seawater is pumped into a sedimentation pond (larger, the better) for initial settling. Salinity permitting, some farmers stock this settling pond with Tilapia to further condition the water. Barramundi or sea bass are also stocked to control the numbers of Tilapia fry from overpopulating the reservoir.

From the settling reservoir, the effluent is pumped to a smaller 2,000 m2 pond or canal with a series of partitions or baffles to further facilitate settling of suspended solids. The effluent overflows to a 2,000 m2 reservoir (lined with HDPE). The effluent overflows or is pumped into a lined, chlorination reservoir (1,000 m2) where the water is chlorinated at 10 ppm active chlorine. Some farmers have duplicate chlorination reservoirs to alternate treatments to insure a continuous flow of treated water. After the chlorine is neutralized (usually 24 hours or less using a paddlewheel), the treated water is pumped to a conditioning reservoir and available for the round-tank module. Stored water in the conditioning reservoir should be used within 3 days before the initiation of algae blooms.

The percent of water renovation can exceed 100% of the tank volume per day...depending on the biomass density, water quality and tank bottom conditions. But generally, the average daily water exchange throughout the grow-out cycle is much less. To insure that there is enough area for water settling, treatment and storage depends on the quality and source of water. If the water source is from sub-sand bore well points or a pristine location, then a reservoir to grow-out ratio of perhaps 1:1 is more than enough capacity. But if the water source is from a brackish water estuary shared by many farms, then more reservoir capacity would be required to allow for settling, treatment and conditioning.

What is Synbiotics?

The concept of “synbiotics” is a technique that is simple yet effective in quickly stabilizing the shrimp pond environment and has proven effective in controlling pathogenic bacterial or disease outbreaks such as APHNS/EMS and Vibriosis. Synbiotics, or the fermentation of complex carbohydrates, is actually an ancient technology but a relatively new technique when applied to shrimp farming.

Synbiotics is defined as the synergy between “probiotics + prebiotics + fermentation”. Fermentation of specific prebiotics, such as rice bran and defatted soy meal, provides the substrate, energy, organic acids, enzymes, and other nutrients to sustain colonies of probiotic bacteria that further stimulate the production of micro-organisms.

This preventative management technique has proven effective in controlling disease outbreaks through stabilization of water quality, pH, phytoplankton balance, soil mineralization, and the reduction of organic material on the pond bottom. The bio-reaction of microorganisms and metabolites fueled by “fermented prebiotics” accelerates the degradation of accumulated organics and out-competes pathogens in both the pond environment and within the shrimp as well.

Synbiotics has been successfully applied in all culture systems... from nursery to intensive grow-out to extensive grow-out systems and at the hatchery level as well.

Synbiotics may be the most cost-effective method of eliminating the use of antibiotics in shrimp farming and is fast becoming a part of the daily operating procedures in shrimp farms worldwide.

Protocol for preparing fermented rice bran:

1. Sterilize the tank and all materials with a chlorine wash (20 ppm) prior to fermentation

2. Disinfect the water using peroxide (.5 ml active ingredient per liter)

3. Temperature of the water should be between 26-34 C.

4. Add rice bran, enzymes, probiotics and buffer to the tank and aerate

5. Check the pH at the end of the 24-hour fermentation process. pH should be at least 6.0

6. Prepare a new batch for each dosage. Do not replicate or inoculate using a prior batch

For semi-intensive farms where access to the ponds or electricity is limited, the fermentation of the rice bran can be done at the pond site without using aeration. In this case, smaller tanks would be mixed manually 1-2 times per day.

Dosage of fermented rice bran in semi-intensive ponds

The recommended dosage of fermented rice bran (FRB) in extensive earthen ponds (stocking density between 15-40 per m2) is 5 kilos per hectare per week to maintain a healthy and stable pond environment. For intensive ponds our round tanks, a 1 ppm dosage every three days is sufficient.

It is highly recommended to start treating the pond with the fermented rice bran prior to stocking (while filling the pond) to initiate the maturation of the water and mineralization of the pond bottom. Following pond stocking, the pond can be dosed once or twice per week depending on logistics and manpower constraints.