vannamei shrimp prawn

Vannamei King Prawn – 4 Months to Harvest in Biofloc System

vannamei king prawn
Vannamei King Prawn

Having being personally involved in the Aquaponics industry for many years, I became intrigued about the Biofloc aquaculture system, as it makes use of some of the same beneficial bacteria as aquaponics to reach balance in water quality parameters.

As with Aquaponics, Biofloc systems rely on beneficial autotrophic bacteria to fix the ammonia generated in the tank by uneaten feed and faeces from aquatic life (which is toxic to aquatic life), into nitrites (also toxic) and finally into nitrates (non toxic).

Nitrates of course, aid in plant growth in an aquaponics system. In a Biofloc system, nitrates help to promote the growth of plant life such as phytoplankton (a micro algae), which fish and prawns, like the vannamei species, feed on.

Another similarity between Aquaponics and Biofloc systems is the use of Heterotrophic bacteria to help with the oxidisation of ammonia and the breakdown of organic matter such as proteins, carbohydrates, fats and ammino acids. In Aquaponics this is usually achieved in a separate off system tank called a mineralizer, whereas in a Biofloc system it all happens in the grow-out tanks

STAC – Sepang Today Aquaculture Centre specializing in Biofloc Systems

I decided to explore more by approaching Mr Khoo Eng Wah from Malaysia (managing director of STAC – Sepang Today Aquaculture Centre) a Hatchery and Aquaculture Training Centre that specialise in BioFloc Aqua Farming.

 STAC is a Malaysian Company registered in 1995. In 1997 they started operations as a Tiger Prawn Farm and Hatchery. In the same year, STAC started offering courses on Tiger Prawn(P.monodon), Grow-out pond and hatchery operation and technical transfer for local and overseas investors and Aquafarmers. They have had participants from all over the world attend these courses, including South Africa, Gambia, Sudan, Kenya, Egypt, Kuwait, UAE, Saudi Arabia, Oman Seychelles, Maldives, India, Sri Lanka, Bangladesh China,Taiwan Japan,USA Australia, Indonesia, Poland, Latvia , Cambodia , Philippine, Papua New Guinea and Singapore.

They present Aquaculture Courses on various species, including GIFT Tilapia, Jade Perch, Vannamei Prawn/Shrimp, Australian Freshwater Crayfish, Hybrid Grouper and Fresh Water Prawn.

Australian Fresh Water Crayfish:
The Australian Fresh Water Crayfish from STAC Indoor
RAS (Recirculating Aquaculture System)
2Kg GIFT tilapia STAC
2Kg GIFT Tilapia at STAC Aquaculture Training Centre, Malaysia

Their Biofloc Technology technical transfer courses for Vannamei Prawn and Tilapia started in 2016. These Biofloc Courses span over 3 days and involve classroom lectures and hands-on practical work.

imhooff cone Biofloc water test
Student getting water samples from Indoor Biofloc Technology System – Courtesy STAC

The Biofloc Technology Courses are generally conducted weekly, though Covid19 has put that on hold at the time of writing this article (May 2020). I asked Mr Khoo Eng Wah if they were considering offering an online course, but he says that they don’t have any plans at this stage as he believes that hands-on training is of utmost importance, if you are seriously considering starting your own Biofloc system.

The Biofloc Technology course offered by STAC in Malaysia, covers:

  • Biology of Vannamei
  • Disease prevention(Vertical and Horizontal transmission) and bio-security quality and SPF (specific pathogen free) pLs (post larvae)
  • Building up the Biofloc using autotrophic bacteria ( nitrogen cycle bacteria) and heterotrophic bacteria(Bacillus,Lactose bacteria,yeast) with the application of carbohydrates such as molasses
What is Biofloc training

After attending classroom lectures on ”Biofloc Technology“ , participants are required to do hands on practical work for BFT water parameter monitoring using simple test kits. Microscope study of the microorganism found in the Biofloc Technology tanks are also done.

Additional Questions on Biofloc system posed to Mr Khoo Eng Wah

Biofloc has become very popular in Asia, but slow in the Western World, why is this?

I think the farming species, such as the marine shrimp are more susceptible to disease, most of the aquaculture farmers in Asia use biofloc for shrimp production to avoid risk of diseases.

What would you say is the number 1 benefit of using a Biofloc system? 

Yes since i started to use the BFT (BioFloc Technology) I have never encountered any disease problem. The micro-organism built up as “floc” are the food for the culture species and help develop the natural immunity of the culture species. Also, the microbes act like an army to fight the pathogenic micro-organisms

What are the biggest challenges or risks in using Biofloc systems?

The BFT (BioFloc Technology) aeration is very important and is SPF (Specific Pathogen Free) pLs (Post Larvae) shrimp or fish fries to avoid disease and potential loss. A reliable primary power source and backup power generator is imperative for Biofloc Technology Aquaculture farming.

Can Vannamei prawns and tilapia be grown out in the same Biofloc tank, or should they be in separate tanks?

In separate tanks

What is the recommended stocking density for Vannamei shrimp and tilapia in a Biofloc system?

Vannamei Shrimp in the nursery can be as high as 2000 pL (post larvae) per m3 for 1-1.5 months then transfer to grow-out tank 300-500 juveniles per m3 until marketable. Tilapia can be 200 per M3 for 1.5 months then reduce to 50-60 per m3 with marketable weight 1 kg per fish.

Biofloc requires a lot of aeration, what aeration system do you recommend, airstones, microbubble generators?

Yes, aeration very important, airstone is old method we use aerotube and rootblower (in fact we help the investors/farmers to set up the aeration system with supply) Engineering design is important

What would be the recommended total pond or tank size (in cubic meters) to make a Biofloc system profitable?

We have offered our service to set up Biofloc Technology in Malaysia, the best is a minimum of 300-500 m3 (cubic meters) Indoor 

From a return on investment perspective and based on your vast experience Mr Kooh Eng Wah, what type of aquaculture species would your personally farm with, tilapia, grouper, jade perch, Australian freshwater crayfish, Vannamei Prawn/Shrimp, Freshwater Prawn? 

My nr 1 choice is Vannamei (4 months to harvest from Larvae & good market price), followed by  Hybrid Grouper (10-12 months) Jade Perch, Fresh Water Prawn and Crayfish. Tilapia is the cheaper fish in Malaysia so ROI is slow.

Vannamei prawn post larvae
Vannamei Shrimp Juveniles – Courtesy STAC Malaysia

Can the Australian Freshwater crayfish be grown in a Biofloc system?

My experiment is still ongoing. No solid conclusion at this stage.

The basics of a Biofloc Technology System

Biofloc Technology is the creation of Professor Yoram Avnimelech from Israel, also known as the father of Biofloc. Professor Avnimelech discovered that one could do high density aquaculture farming of tilapia and shrimp in a RAS system by neutralising inorganic nitrogen in these system by the addition of carbon in the form of carbohydrates such as rice and molasses. This is termed as maintaining a optimum Carbon to Nitrogen Ratio (C/N Ratio) for good water quality, conducive to reduced feed costs and faster growth rates of the farmed aquatic species without the need for major water changes that are otherwise the norm in standard RAS aquaculture systems.

Biofloc microbial rich brown water
What is Biofloc Technology?
It is the use of beneficial microorganisms accumulated as a “floc” in “aquaculture systems” to control water quality and to achieve production goals.

In short, the addition of carbohydrates to feed the beneficial bacteria, leads to the control of inorganic nitrogen (i.e. ammonium), and through the resulting assimilation of nitrogen from the water, by the synthesis of microbial proteins. These produced microbial proteins are eaten up by the fish or shrimp. This of course leads to the reduction of feed costs. In addition it has been found that the protein content of feed can be reduced to a mere 20%, leading to additional savings when compared to the more expensive high protein commercial feeds.

Biofloc technology - Protein Flocs

In a Biofloc system, Autotrophic bacteria convert organic waste such as faeces and uneaten
feed into Ammonia Nitrite and Nitrate and the heterotrophic bacteria convert the nitrate with the addition of carbohydrates such as tapioca,rice, sugar or molasses into the biomass of the bacteria which forms a group of beneficial micro organisms. The brown colour of the water indicates a good balance of beneficial bacteria and micro organisms.

Biofloc Systems Best done Indoors or under Cover

Biofloc Technology RAS systems are generally indoors or under cover. If it were done outdoors rain water would negatively affect the critical balance of the microorganism “flocs” in the tanks.

Indoor Biofloc Aquaculture RAS system
Indoor Biofloc System Malaysia – Photo Credit” STAC

It is imperative however that indoor and under cover Biofloc systems receive enough light for photosynthesis to occur leading to the creation of phytoplankton, also known as green water. Without light, there is no photosynthesis. Though artificial lighting could be used for an indoor system, it adds to the operating costs of the system, decreasing the potential return on investment. The most economical way is to have a greenhouse plastic structure over the ponds or tanks.

Indoor Biofloc Vannamei farm
Taizhou Indoor Biofloc Vannamei farm: Photo Credit STAC, Malaysia

Benefits and Challenges of Biofloc Technology

Benefits of Biofloc Technology

  • Allows for high density farming of tilapia and prawn/shrimp
  • Reduces the risk of pathogens and basically eliminates disease (beneficial autotrophic and heterotrophic bacteria attack any pathogens)
  • Controls ammonia and other inorganic nitrogen by addition of carbohydrates (carbon)
  • Reduces FCR (food conversion ratios), thus reducing feed costs and increasing profits
  • Eliminates feed waste as all is basically recycled in the system leading to between 25%-30% savings in feed costs.
  • Water Savings – No or Negligible Water Changes. Very important as water becomes scarce in many parts of the world

Challenges of Biofloc Technology

  • Can be capex intensive to start as it needs to be under cover & have adequate electrical backup
  • Requires intensive Oxygen (aeration) 24/7. If this fails, expect huge losses of the farmed aquatic species in minutes.
  • Labour intensive. Needs constant daily management and monitoring of water parameters.

Understanding the beneficial bacteria in a Biofloc system

There are basically two types of beneficial bacteria in a Biofloc system, namely:

  • Autotrophic
  • Heterotrophic

Autotrophic bacteria fix inorganic nitrogen. Without these in an aquaculture system, ammonia levels would rise in tandem with the accumulation of uneaten feed and excreted faeces from the aquatic species and kill the fish or shrimp as it is toxic. Ammonia (NH4) is oxidised into Nitrite (N02) by the Nitrosomonas bacteria. Nitrite however is also toxic to fish and shrimp. The Nitrobacter bacteria then oxidises Nitrite into Nitrate (N03). Nitrate is not toxic to fish and will aid in the production of plant life through synthesis of light resulting in phytoplankton (micro-algae) which also serves as food for the fish and shrimp. Autotrophic bacteria are also known collectively as nitrifying bacteria.

Heterotrophic bacteria are the decomposers of the world. Their job is to fix organic matter such as proteins, carbohydrates and fats. Other than assimilating ammonia they also convert uneaten feed and faeces into microbial proteins that form as “flocs” in the water. These microbial proteins are eaten by the fish and shrimp. Heterotrophic bacteria require plenty of Dissolved Oxygen to do their job.

Though all of these bacteria are naturally occurring over time (i.e nitrifying bacteria take up to 6 weeks to establish themselves), almost all of the Biofloc farmers seed their system with Probiotics to speed up the process of bacteria production. Probiotics are usually in powder form and the bacteria will only be activated once the probiotics powder is added to the water.

The need for aeration in a Biofloc system

Dissolved oxygen is essential for the aquaculture species being grown and for the bacteria to do their job.

To infuse oxygen into the water of tanks and ponds, aquaculturists around the world use airstones, aerotubes or nano-bubble generators driven by compressors, air pumps or blowers. Water splashing back into the tank or pond also helps to infuse D.O. into the water. In larger ponds, motorized paddles are used to churn up the surface area of the water.

aerotube micro bubbles biofloc aquaculture aeration
Aerotube producing micro bubbles

Another function of the airstones and aerotubes in a Biofloc system is to ensure that any uneaten feed or biomass in the tank does not come to rest and accumulate at the bottom of the tank. It is advisable therefore to keep repositioning the airstones and aerotubes at the bottom of the tanks and ponds to prevent the accumulation of biomass in a specific spot, that can lead to anaerobic dead spots that put additional pressure on oxygen resources within the tank or pond.

So what do you need to start a Biofloc aquaculture farm?

Fish Tank or Pond : Many biofloc farmers use round PVC liner tanks with reinforced wire mesh wall. They are inexpensive and can last up to 10 years or more. If using a pond, then line it with PVC sheet so that the acidity in the soil does not affect the pH and other water parameters in the pond. Before starting off your pond, it is recommended that you disinfect the inside of the tanks and all equipment and accessories including airstones, with Potassium Permanganate(KMNO4)

Biofloc Pvc liner tanks with steel mesh reinforced walls
Pvc liner tanks with steel mesh reinforced walls

Aerators, Compressors or Blowers: As already discussed, aeration is of utmost importance in a biofloc system. Always have a spare air pump or blower as a backup in case of emergency

Airstones, Aerotubes and accessories: Always have plenty spare aerotubes and airtsones for when needed. They tend to block over time, so will need replacement at some stage.

Power Backup System: Biofloc systems need constant power 24/7. If your mains grid power supply goes down you need a backup power source. Diesel generators are the most reliable for long operation. Solar power with battery storage for night operation is also good, but can be expensive, especially the battery banks.

Probiotics: To speed up the presence and concentration of bacteria

Carbohydrates: Required for adding carbon to the system and stabilising the C/N ratio to optimum biofloc system levels as already discussed previously in this blog post.

Ammonia, Nitrite and Nitrate Test kits: Measuring these levels regularly will help ascertain the effectiveness of the autotrophic and heterotrophic bacteria in your biofloc system and aid you in taking steps to correct any issues as a result.

Water Hardness (KH) and Iron(Fe) Test kits: To measure alkalinity or carbonate hardness of the water for pH stability and iron content.

water hardness and iron test kit JBL
Example of water test Kit for Nitrite, Nitrate, Water Hardness (KH) and Iron (Fe)

Dissolved Oxygen, pH, and Temperature meters: These meters are essential for a Biofloc system. The measurements affect the health of the aquaculture species and should thus be measured daily to correct from any deviations from the optimum. Meters with a combination of the above readings are available. Alternatively, get a meter for each specific parameter. Dissolved oxygen levels in Biofloc tanks or ponds should be kept above 5 mg/l.

Calcium Carbonate or Calcium Hydroxide: Calcium helps raise pH levels and acts as a PH buffer. Nitrifyng bacteria will overtime lower the pH level in the system, so a buffer is required to balance the downward pressure on pH over time.

Sea Salt: To maintain the required salinity level in the water. The general recommended dosage is around 1Kg of sea salt per 1000 litres of water in the tank or pond.

Potassium Permanganate(KMNO4): A good sanitiser for tanks and equipment in a Biofloc system as it kills pathogens. Also used for removing Iron from water.

Imhoff Conical Measuring Beaker: Gives a visual representation of the Floc level in the water

Imhoff Cone Beaker biofloc measure
Imhoff Conical Beaker used to visualise the concentration of FLOC in the water

The Imhoff cone is used to collect a water sample from the tank or pond at a depth of around 20 cm. The solids in the water within the cone must then be left to settle for 20-30 minutes. Solids will attach themselves to the side of the cone making it easy to do a count of the approximate micro proteins flocs in the tank.

The concentration of bioflocs in the tanks and ponds will quickly increase within 2-6 weeks to over 10 billion beneficial bacteria per cubic centimetre, a true marvel of nature.

Carbohydrates for maintaining good C/N Ratio: The colour of the water in your Biofloc system is also a clear indication of where its sits in terms of Carbon to Nitrogen (C/N) ratio. As previously explained Carbon, in the form of carbohydrates (with C/N ratios of greater than 10:1) such as sugar and molasses have to be added to the system in order to neutralise Nitrogen (i.e. ammonia) to ensure good water quality. Also ensure that the shrimp and fish feed has a C/N ratio of around 10:1. An additional method to increase the C/N ratio is to use feed with a low protein content, no more than 20% (many commercial fish feeds have a high protein content of 30% plus). Ideally, one wants a C/N ratio in a Biofloc System to be on average 14:1

Why add carbohydrates such as molasses to biofloc systems
Carbohydrates (Molasses) being measured to maintain good Carbon to Nitrogen Ratio

When the Biofloc system is first started, the water colour will start taking on a green tinge. This is the result of sunlight’s photosynthesis effect in the promotion of plant growth such as micro algae (phytoplankton). As carbohydrates are added into the system to feed the beneficial nitrifying and heterotrophic bacteria and as the bacteria colonies increase in density, the water will start turning to green/brown, then brown/green and eventually to different shades of brown. Brown water indicates a good concentration of bacteria in the system (i.e. increased microbial community).

Green water biofloc system aquaculture phytoplankton
Green Water Culture – MicroAlgae photosynthesis

Hands-on Biofloc Training

We trust that the above article has given you a good perspective on the benefits and possible challenges of the Biofloc system. There certainly is a lot of evidence now that Biofloc is an advantageous alternative aquaculture system, predominantly for Tilapia and Shrimp, in terms of improved FCR (food conversion ratios) when compared to non-biofloc aquaculture farming methods.

As Mr Khoo Eng Wah from Malaysia (managing director of STAC – Sepang Today Aquaculture Centre) puts it, “The theory is a good start, but nothing beats hands-on experience”. The Biofloc Technology course presented by STAC in Malaysia puts a lot of focus on the practical side, getting participants to do the water tests, prepare the feed, handle the aquaculture species and thus learn from actually doing it.

Biofloc water testing
Student at the STAC Biofloc Technology training Centre doing water tests in the lab

I would like to thank Mr Khoo Eng Wah for his time and kind contribution to enable to write this article and for supplying us with most of the photos displayed herein.

For more information on the Biofloc Course presented by STAC in Malaysia please contact Mr Khoo Eng Wah. Details here

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