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CTTI-BCSIR has been working with RAS (Recirculating Aquaculture System) for more than a year. We have arranged weekly plant visit since then. We talked with the visitor, learned and discussed about their queries regarding RAS. There are several questions that were asked several times. We think those questions worth sharing with you to make the technology and its related issue clearer.
Here we have gathered the frequently asked question from the visitor regarding RAS. Here is a short list of them. More will come accordingly.

What is the least size of RAS which is economically viable?

With perspective of Bangladeshi market and availability of machinery, at present 170-180 m3 is considered as least economically viable for China based machinery and 100-120 m3 for European based machinery. If machineries can be produced locally it will definitely decrease.

How much land area will be needed for these sizes?

What will be the total project cost?

170-180 m3 China based machine will cost approximately 60 Lakh and 100-120 m3 European based machine will cost 1 crore 40 Lakh Taka.

How much fish I can produce in 170 m3 system?

In rough estimation 30 ton of catfish can be produced yearly. (Safety margin have been considered)

Ok, But, how much fish I can release per Liter?

Alright that will depend on your targeted harvest size. RAS works on the basis of body weight as feed is in proportion with the body mass. So, in previous calculation, we suggest approximately 60 kg/m3. Here 1m3 equivalents to 1000L. So, if my desired harvest size is 1 kg. I can release 60 fingerlings per 1000L of water.

How much electricity will it cost?

According to current design China base company will require approximately 8-9 kW/h for 170-180 m3 system and European machineries will require approximately 12 kW/h for 100-120 m3 system. So you would need to arrange a generator accordingly (15 kVA or more).

How much liters of water needs to be circulated each day?

RAS will require recirculation of all the water available in the system within approximately 1 hour. This is the basic/ thumbs rule. Some company design varies within +/- 10%.

How much water need to be added as makeup water daily?

Around 4-10% of the total volume on daily basis water will be needed daily.

Where can I build the facility?

RAS can be built anywhere as it requires less land for a higher production of fish. But one has to ensure 24/7 supply of Electricity, Generator (in case of failure), Seed (fingerling) availability and easy marketing. So, it is not technically feasible to set up RAS in remote area. Location near big market with good supply of electricity and seed (fingerling) availability is preferred.

What type of species can I grow in aquaculture?

Almost every kind of fish is suitable for RAS. But as it is comparatively costly to operate RAS, it is better to stick to high market value and high demand species. Approximately you can go with the species with a stable market price of at least 350-400 tk/kg. Till now Tilapia (not viable due to low price), Catfish (Pabda, Sing, Magur, Shol etc.) have been proved suitable for RAS in Bangladesh. (Tested at CTTI-BCSIR)

Can I grow only Freshwater species in RAS?

No, you are free to choose between fresh water and salt water/marine. Machineries will be designed accordingly. Extra unit may need to control salinity in case of cultivation marine species where sea water is not available.

Does the fish stay in the same tank till being harvested or is it required to change the tanks?

That will mainly depend on you. You can rear fish in any of these two systems. In case of same tank, you have to change the filter mesh of the fish tank, ensuring maximum possible hole size to ease removal of fish waste. In case of fixed size tanks, one has to sort out time to time accordingly. But be careful while handling fish of any injuries or external parasite introduction.

How long does it take to build an RAS facility?

A recirculating aquaculture systems facility takes about 12 months (for custom made design) from the initial design to system start-up. Factors such as species and location will influence the time it takes.

What are the advantages of recirculation aquaculture systems?

• Stable production of high quality fish, 365 days a year • Low water requirement. • High production of quality fish on a relatively small area. • Reduced risk of diseases. • Low mortality rates. • Continuous control. • No environmental influences. • Intake and effluent reducing to the minimum. • Treatment of discharge water.

What are the challenges of recirculating aquaculture systems?

• Depending on regular power supply and control. • Start-up capital for building, technical installation and running cost.

What are the main parts involved in RAS?

• Fish rearing Tank (to hold fish) • Mechanical Filter (to remove solid waste) • UV Filter/Reactor (to kill parasites) • Circulation Pump (to recirculate water) • Biological Filter (to convert Ammonia) • Degasser (to remove Carbon dioxide) • Oxygenation System (to mix oxygen)

What parameters we would need to check frequently?

• *O2 (Multiple times in a day) • pH (Multiple times in a day) • NH3 (Daily) • NO2 (3 day in a week) • NO3 (Weekly) *Most important

Do I need pure oxygen to supply?

It is not compulsory. But supply of pure oxygen can ensure Faster growths rates, Better FCR, Less stress and diseases, Higher quality etc.

What is the FCR possible in RAS?

Generally, FCR 1.3-1.4 can be obtained in RAS, better can be also obtained if system can be operated effectively.

How long it will need to reach break-even point?

The project (China based) will reach break-even point before its 3rd year of operation. European system may require some more time to come to break-even point.

From where we can buy RAS now?

Unfortunately, currently there are no renowned producer of complete RAS system in Bangladesh to our knowledge. Some people are producing it on their own but no successful case studies have been reported to us till now. Be careful and think before you invest. At present There are many industries producing RAS in China and many other different countries like Netherlands, Denmark, Norway etc. You can contact the company over the internet. Read their reviews, learn about their successful stories before buying. If you are confused and cannot come to a decision. You can contact CTTI-BCSIR for specification review and suggestion.

I am a student; can I do this?

Yes, obviously you can do RAS. But to make it economically viable, there is a minimum size mentioned earlier, which requires good amount of money to invest. But you can definitely do it for your own research project not for business.

Can I do RAS on rooftop?

Again, yes you can do it as a hobby (small scale) not for commercial purpose. It will include heavy machineries and water volume, which we do not suggest at all.

What types of manpower we would need?

Where can I get the Training?

In Bangladesh there are several farms running RAS at present. One of them is at CTTI-BCSIR. Which also provide Technical Training and On-site support to the people. The training schedule will be given at and Keep in touch.

I need a Project profile. Where I can find one?

You can also find a feasibility study with your custom-made project profile. It will cost 5000 Tk to have a feasibility study report on RAS from CTTI-BCSIR. You have to apply for feasibilities on an official pad (if any) and come at the office. (BCSIR, Engineering Division Building, 1st floor and ask for CTTI office).

I want to start RAS, what should I do?

Good. Now you have to choose a location suitable for RAS. Please make sure you can provide enough energy and have a good market. You can contact with the RAS provider over the internet.

Can I run RAS from Solar Power?

It does not matter. If you can ensure 24/7 hours supply of electricity, you can go for it. You can use solar, wind whatever you like. Just for your information to go for it, please keep in mind some of the parts (in existing design) may need three phase electricity. So, design your electrical source accordingly.

How much time I will get to react if anything goes wrong?

Generally, if you are running at full density you may get around 20-30 min to response properly. It may lessen due to water quality issue.

What are the thing I can prepare for emergency case?

The most vulnerable parts are the pumps, oxygen supply. So, have some pumps standby with piping ready. Buy a generator and some liquid oxygen cylinder with proper connection.

Can I avoid drum filter?

No, if you want to build a full functional RAS, you will definitely need drum filter.

Do I need light? Is it enough instead of sunlight?

There is no data available till now to show the impact of light on fish growth in RAS. Till now no effect has been discovered or reported. So, light cycle has no effect on fish growth, But, intensity of light has. Very bright light will make the environment uncomfortable for fish. It is recommended to use medium intensity light. Main purpose of light is to watch the behavior of fish for any kind of unusual things. Some industries use submersible light, this also make the place looks amazing!! Some company claims That light can be used for a range of applications like fish farming, fish fattening & conditioning, fish attracting, fish spawning, coral growing, algae growing, water tanks, docks & marinas. But no scientific data is available till now.

What about the taste of the fish reared in RAS?

The taste of fish cultivated in RAS is fantastic. Not only the taste but also the nutritional values are also great (tested at our LAB).

What Chemicals are needed?

Luckily, there is no need to add chemical once the system is ready for fish cultivation. Initially for Bacterial growth in biofilter, some chemicals are needed but once in operation, no need to add more.

How much is the Import Tax and Vat of RAS machinery and parts?

HS Code: 84194090; Duty-1%; Vat-15%; AIT-1%

What services can CTTI-BCSIR provide?

We do 1. Feasibility Study/ Project profile, 2. Technological Support, 3. On-site machineries Training, 4. Workshop and Training program, 5. Consultancy etc.