Optimizing tilapia biofloc technology systems, part 1

Published on: 07/31/2018
Author/s : Ramon M. Kourie / Chief Technical Officer, SustAqua Fish Farm.

Engineering design at Chambo Fisheries, the world’s largest biofloc tank farm for tilapia Battery of eight multi-cohort sequential continuous culture BFT tanks at Chambo Fisheries.   Experience raising tilapia in biofloc technology (BFT), where aerial feeding rates are at least four to five orders of magnitude greater than in shrimp BFT systems, is limited. Areas that are particula...

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July 31, 2018

Good Day Ray

I am finding this concept fascinating. The multicohort, leading to partial harvesting, was something that I modeled for our Dusky Kob and it makes economic sense.

I am intrigued to find out in practice how the screens, that are used to divide the tank for the different GSs, impact on the flow rate and subsequent solids removal.


Do you also have any metrics to share on the percentage oxygen saturation that these systems run at under optimal stocking and Biofloc levels?

Regards
Neil

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July 31, 2018

Hi Neil

The only way to maximize throughput production relative to maximum carrying capacity is via the management of a single tank system as a multi-cohort sequential stock management system. This we call the Production: Capacity Ratio (P:C ratio). Apart from reduced CAPEX per unit fish production, the benefits filter down to energy costs for aeration, carbon dioxide stripping and horizontal water movement where power costs are basically halved when compared to a batch production system.
As far as water velocities are concerned there are two aspects that require hydraulic calculations 1) the frictional drag forces of the moving water mass which occurs at the wetted surface area (walls and floor) and 2) the frictional drag forces which occur through the screened compartments. The sum of which is called the system hydraulic gradient against which horizontal water movement needs to be balanced to achieve the design water velocity.
Screen selection, number of screens, % open area are all important affecting the final hydraulic gradient. An offset bottom bar raised three inches from the tank floor and the use of a round bar or cable to achieve complete closure of the screen are the tricks of the trade preventing solids collecting at the floor-bottom bar of the screens.

At velocities of 25-30cm/sec, the movement of heavier solids (dead material, fibrous material) the heavier material drifts on the tank floor at velocities around 15-20% slower than the water column velocities - movement is still achieved. Industrial aquaculture involves a significant amount of engineering design, hydraulics, fluid mechanics, thermodynamics, heat transfer etc. The objective being to produce fish sustainably at the lowest possible cost capitalizing on the benefits of scale economies. At 1130m above sea level we opted to run at 4.5mg/L while the added cost to take dO2 levels to 5mg/L was not great but not essential - calls for added floor diffusers. The combination of paddlewheels and floor diffusers greatly improved the driving gradient in R-ended tank systems increasing oxygen transfer efficiencies under field conditions. Our next project using sea-water BFT for O. mossambicus will, in addition, carry a nano-bubble aeration system to pick dO2 levels up into the 75-85% saturation range. Hope the above is satisfactory for now.

Best, Ray.

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August 1, 2018
Thanks Ray for a detailed reply, greatly appreciated.
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September 24, 2019

Hello Ray could you do the experiment with Nano bubble generator what was the result?

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September 24, 2019
Hi Harish. The problem with nano-bubble aeration is that it does little to remove other gases (gas stripping) such as carbon dioxide in the water mass in BFT. Also when the nano-bubbles collapse they release allot of energy due to the internal pressure within the nano-bubble. This concerns me as this could impact on the bacteria. One study in Japan confirmed my fears on this. I think the safest application for nano-bubble technology is in an aquaponics environment where the plants could benefit from higher oxygen levels around the root zone. Apart from in an aquaponics set-up I've abandoned all further work on nano-bubble technology due to the reasons shared here. Best, Ray
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September 25, 2019
Ramon Kourie
Could you please share the Japanese study you referred to? Best, Kolbjorn
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September 25, 2019
Hello ramon, We have been using our systems in Aeration tanks of ETP’s and lagoons with fantastic results and savings of energy....Flocs were more stable...Very curious to hear about the Japan project as something seems to be missing....
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September 25, 2019
https://m.english.vietnamnet.vn/fms/society/195633/hi-tech-methods-raise-production-value-of-farm-produce--hcm-city.html#ui=mobile


50 tons/ ha/ cycle using Biofloc and Nanobubble technology....
Reply
Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
September 26, 2019
Hi Kolbjorn.I wll look for the Japanese study hen revert.
Best, Ray
Reply
Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
September 26, 2019
Hi Harish
If you can get 50t/Ha/crop of shrimp using nano-bubble aeration technology then I've got to hop onto a an airplane to see your set-up. I'll be bale to promote your initiatives.
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October 22, 2019
Hello Ramon , Interesting , but certainly not impossible ... I have people doing 3.5 kg/ M2 consistently using blowers etc...

Right monitoring ,constant supervision And superior aeration 5kg/ M2 is certainly doable...

I will keep you informed with our systems and also we are a setting up our own completely integrated RAS will get you info on that too...

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Pannita Seareaw Pannita Seareaw
Student
September 4, 2018

Nice forum! I will share it with all of my friends.

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November 18, 2018
need some help

need small production capacity project report for fish culture using BFT
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November 18, 2018
RAJENDRAKUMAR SHINGALA, SUPRINTENDENT OF FISHERIES, GUJARAT FISHERIES, GUJARAT, INDIA

Please mail me with the particulars of the request to .
Reply
Vijayakumar Patibandla Vijayakumar Patibandla
Marketing Manager
December 5, 2018

Please give complete practices of farming as some of the farmers are interested to go for Tilapia (TBT) on low salinity areas of shrimp ponds proposal of conversion.
Regards.

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March 14, 2019

What is the costing in Bioflock system project?
And what is the cost of production and yield?

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July 3, 2019
Plz.give me information about bioflok fish farming cost of production and profit and duration of production

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August 13, 2019

Kindly need project report on farming gift tilapia in 65000ltr using BFT

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September 19, 2019

Sir
I have around 35 cent land with 2500 sqft shed. I want to do Biofloc system first on trail basis before going into 100% commercial. As trail I want to go for 3 tank with 13 to 15000 liters tank. I am thinking of doing three varieties of fish ie.pearl spot, Mono sex tilapia and rohu, pls advice if it's ok or should I change my plan. I want a project report for the same, will it be possible for you to get me a report to present the same to the bank? My e-mail is sunnyamarpi03@gmail.com. regards

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September 20, 2019
Would like to know more on optimising tilapia Biofloc.
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September 24, 2019
Yes would like to know more. Also advice how much density I can go in a 10000 ltrs tank in case of tilapia and what density for Anabas.
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Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
September 26, 2019
To all interested Engormix list members.

I'm afraid I'm always under pressure and cannot always answer your questions. I am busy writing a book to be called, "A Guide to Tilapia Production in Biofloc Technology (BFT) Systems". I wont be covering shrimp BFT production as there is already a good publication available through the World Aquaculture Society (WAS). My mission is promote tilapia production using sustainable intensification systems, BFT is one of them, as means to produce tilapia at a cost of US$0.90/kg - by 2050 there will be over 9 billion people sharing the planet...BFT could be one of the answers.
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January 16, 2020
Dear Ramon, Yes, efficient aeration using nano bubble aeration will help promote the proliferation of beneficial aerobic enzymes and bacteria to live in an aquatic environment. beneficial aerobic enzymes and bacteria will naturally reduce organic loads in an aquatic environment. I think the air bubbles really nano , implodes and transfer the gas to the medium, and the rest rises and burst on the surface allowing more residence and contact time. http://anzaimcs.com/en/main/examplenanobubble.html , Ex: nanobubble japan. Best regards. Sanu Jose .
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January 16, 2020
Dear Ramon, All the "Best Wishes" on your oncoming book "A Guide to Tilapia Production in Biofloc Technology (BFT) Systems" expect it to be path breaking as your "chambo fisheries" innovation, .really looking forward to it. Any new project modifications on the chambo model, what was limitation on higher stock density DO or TAN or other ? 40kg/m3 would have been "GREAT" because you had total control over culture water {almost a RAS) . Can share what was on your mind? Best Regards, Sanu Jose.
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January 16, 2020
Hi Sanu

Thanks for your comments. I believe the need for efficient gas stripping, particularly CO2 levels, from BFT culture water, which requires conventional aeration and possibly the use of a combination nano bubble system may have some merit. This will require elaborate testing in a research environment prior to commercial use. A control will enable the merits (or not) of the use of nano bubble under BFT conditions to be understood. Best, Ray
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January 16, 2020
Hi Sanu. Using the same design architecture to that developed at Chambo Fisheries we are busy on a 250 tonne per annum BFT multi-cohort sequential system which will run at 35ppt (seawater) raising Mozambique tilapia (O. mossambicus). The sub-surface aeration system will drive the needed horizontal water movement to achieve 30cm/sec current speed, strip CO2 and add dissolved oxygen very efficiently. Power use will come down to around 1kWh/kg of fish production due to the enhanced effect of increased aeration efficiency under saline conditions where the alpha factor climbs to 2.5 at 35ppt. Once this new system is put into use the results will be in the new book, "A Guide to Tilapia Production in Biofloc Technology (BFT) Systems" which will follow. Best, Ray
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January 16, 2020

Hi Ray, Thanks for the reply, wish all success on your 250 ton/year BFT upcoming facility,
Where is the location? What is the stocking density proposed? Directional aeration and circulation with airlifts? Solids removal and PH enhancement with settling tank? Oxygen dosing with "U" tube oxygenation of culture water to 8 ppm for higher stocking density, these were some that came to mind after reading about chambo BFT growout facility, Best regards, Sanu.

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Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
January 17, 2020
Hi Sanu.We wont try to enhance density as there is a correlation between density and FCR's that was apparent in the Chambo Fisheries BFT tank systems operating at 16-22kg/m^3 (as a function of fish size. Rather through further design optimization the aims are to use less power via a more efficient sub-surface diffused aeration system and elevated horizontal water movement from 20cm/sec to 30cm/sec at reduced power input and larger scale and deeper tank systems using seawater and O. mossambicus targeting 1kWh/kg of fish production. best, Ray
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January 23, 2020
hi, Ray , Great work, what is the logic for higher water movement? better mixing and suspension of the floc? wont the fish be over exercised? affect harvest weight and FCR? is'nt tilapia natural in passive or slow flowing water? any cultured custom probiotics used in feed and water at "Chambo"?? here we are consistently getting 0.7-0.75 FCR in round BFT tanks with co settling tanks, (4 months 300-350 gms harvest, 30% CP feed, "GIFT" fish seed, high airlift aeration.) 25 kg/m3. Regards. Sanu.
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Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
February 15, 2020
Hi Sanu

Did you include your carbohydrate source in your calculation of FCR's? This would be the most pragmatic approach to take. I would be keen to learn how much you carbon source adds to your FCR.

Best
Ray
Reply
Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
January 24, 2020
Hi Sanu.

A recent study entitled, “Effect of Water Velocity on Tilapia, Oreochromis niloticus Fingerlings Growth Parameters and Body Composition” (Belal, 2015) looked at horizontal water velocities in fingerling Nile tilapia production. A velocity range of 20-35cm/sec was considered optimal, although lower FCR’s were recorded at a velocity of 25cm/sec as opposed to 35cm/sec where the higher velocity resulted in larger weight gain at the expense of FCR’s. A number of studies have indicated that smaller fish benefit from higher water velocities relative to their body length and smaller fish due to their higher metabolic rates are capable of 1.5-2 BL/sec while larger fish require a reduction in water speed (0.4 to 0.8BL/sec) due to their slower metabolic rates.
It seems as though a water velocity of around 30-35cm/sec would optimal for grow-out operations raising fish over 20g to harvest (>500g). Swimming energetics and the Cost of Transport (COT) is a fascinating avenue of study. In a follow-up commentary I'll explain the the merits of reduced FCR's and enhanced growth under moderate water velocities (as above).
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Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
January 24, 2020

Hi Sanu

Further to my comments above.

It would appear that moderate training actually reorganizes metabolism so as to spare the muscle [against muscle loss] in many teleost's including tilapias (Belal, 2015) with the result that protein growth is promoted over lipid growth in fish that are both fed and continually swum (Christiansen et al., 1989; Lauff and Wood, 1997). The Belal (2015) study indicated reduced body lipid proximate analysis at velocities of 25-35cm/sec. which supports the below hypothesis. In view of a great deal of convincing literature that net protein accretion rates, protein conversion efficiency from the diet, and overall growth rates are all improved if fish are continually swimming (Houlihan and Laurent, 1987; Christiansen et al., 1989; Davison, 1989, 1997), it seems likely that the exogenous fraction of nitrogen excretion will be lower if fish swim aerobically while feeding; that is, amino acids from the free pool will be funneled preferentially toward protein synthesis, rather than toward deamination and oxidation. Because feeding seems to preferentially elevate the concentrations of essential amino acids in the blood plasma (Brown and Cameron, 1991; Espe et al., 1993), whereas swimming preferentially elevates nonessential amino acids (Barton et al., 1995), it may be that the combination is most effective in stimulating protein synthesis. Interestingly, the Specific Dynamic Action (SDA, a measure of protein accretion) effect of feeding continues unabated (Beamish, 1974; Alsop and Wood, 1997) or may even increase (Muir and Niimi, 1972; Blaikie and Kerr, 1996) during sub maximal exercise. Because SDA mainly represents the cost of elevated protein synthesis, this indicates that carbohydrate or lipids are used to a greater extent, not only to power exercise itself, but to power protein synthesis during exercise. This hypothesis then explains the results of the Belal (2015) study.

Reply
Ramon Kourie Ramon Kourie
Agro Engineer Zootechnist
January 24, 2020

Hi Sanu

Last comment. It is often erroneously believed that ALL solids require to be kept in suspension in BFT systems raising tilapias. Our BFT design is selective allowing heavier solids (10-20min settlement time in an Imhoff Cone) to drift on the tank floor which enabled their easy removal from the tank system once a day. While floc was less dense at required 30-35min to achieve a terminal reading using an Imhoff Cone. The objective in BFT is NOT to lose the valuable floc but rather to enable the removal of heavier solids which includes fibrous material and has little more to add in terms of benefits in a BFT system. Proper BFT system design would require careful selection and matching tank hydrodynamics with aeration system selection such that floc is continuously suspended while the heavier unwanted material remains easily removable without impacting on floc volumes. We were able to routinely achieve FCR's of 1:1 on a 20% protein diet under large scale conditions (766m^3 rearing volume) BFT tanks using the system architecture set-up for Chambo Fisheries which applied the above design philosophy.

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February 29, 2020
I am interested in shrimp farming thru BFT...would like to know about its feasibility and investment part and economics of the project .can anyone guide me or End me details on sbshedge@gmail.com? I am partner in Shantadurga aqua products.Tiger prawns farming has been done in the past now intend to restart with vannmie culture thru BFT . technology
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