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Benificial Bacteria - Bio-floc
Eric De Muylder
Eric De Muylder’s Experimental
Shrimp Farming System
On September 26, 2009,
at the World Aquaculture Society meeting in Veracruz, Mexico, I interviewed
Eric De Muylder
(or see this information at the bottom at this page - Liem Tran added), owner of CreveTec bvba, which does shrimp farm and feed consulting around the world. We talked about an experimental shrimp farming system that De Muylder is developing in Belgium.
Shrimp News: How much production do you get from your system?
Eric De Muylder: In four and a half months, I produced 18 kilos of shrimp from a two-cubic-meter tank. That’s the equivalent of 90,000 kilos per hectare per crop. I harvested because I thought the density was getting too high and I was afraid that all the shrimp might die suddenly. But the animals were in great shape when I harvested them, so I probably could have pushed production even higher. Since I don’t have automatic oxygen controls on the system yet, I wanted to make sure I had live animals at the end of the cycle.
Shrimp News: What are your plans?
Eric De Muylder: I plan to build a 9,000-cubic-meter commercial farm somewhere in Belgium. I have a potential investor that has the funds. That project is moving along quite nicely right now. But before that project can get started, I need to do some more trials with my system to double check the numbers and equipment. I’ve run a couple of trials that failed because of equipment problems. So before I do a commercial project, I’m going to run some trials with better equipment and controls.
Shrimp News: You attribute a lot of your success to the biofloc reactor that you added to your growout tank. Tell me a little about that reactor.
Source: Eric De Muylder. Interview by Bob Rosenberry, Shrimp News International. Veracruz, Mexico. September 26, 2009.
Belgium
From The Shrimp List
Shrimp News: How much production do you get from your system?
Eric De Muylder: In four and a half months, I produced 18 kilos of shrimp from a two-cubic-meter tank. That’s the equivalent of 90,000 kilos per hectare per crop. I harvested because I thought the density was getting too high and I was afraid that all the shrimp might die suddenly. But the animals were in great shape when I harvested them, so I probably could have pushed production even higher. Since I don’t have automatic oxygen controls on the system yet, I wanted to make sure I had live animals at the end of the cycle.
Shrimp News: What are your plans?
Eric De Muylder: I plan to build a 9,000-cubic-meter commercial farm somewhere in Belgium. I have a potential investor that has the funds. That project is moving along quite nicely right now. But before that project can get started, I need to do some more trials with my system to double check the numbers and equipment. I’ve run a couple of trials that failed because of equipment problems. So before I do a commercial project, I’m going to run some trials with better equipment and controls.
Eric De Muylder:
Airstones. In a commercial operation, I would probably use
AeroTubes.
Shrimp News: You attribute a lot of your success to the biofloc reactor that you added to your growout tank. Tell me a little about that reactor.
Eric De Muylder:
What I’ve tried to do is exercise some control over biofloc production. If you put shrimp and feed in a tank, you will get some floc production, but the floc will develop slowly. You can accelerate its development by adding floc from another tank. If you add sugar or a carbon source, you get explosive floc production that can get out of control and cause a drop in oxygen. Another way of starting a tank is to keep a separate biofloc reactor within each growout tank. My bioreactor occupies about five percent of the growout tank. In the reactor, the bioflocs continue to remove ammonia from the water and produce food for the shrimp. You benefit from having a lot of floc in your system, without heavy floc loads in your growout water that can interfere with growth. In batches, I pump water from the main tank into the bioreactor. The floc settles to the bottom of the reactor, and the clean water from the top of the reactor returns to the growout tank.
In my system I’m not adding sugar, so I get a combination of heterotrophic bioflocs, which convert ammonia into proteins for the shrimp, and autotrophic bacteria, which convert ammonia to nitrite and nitrate. If you’re working from one cycle to the next and dumping your water, the nitrate build up is not a problem. You might have 150 ppm of nitrate after five months, but, if you kept it going for a couple of years, it would rise to 500 ppm or higher. When nitrates get that high, something will happen and the system could crash. Even though nitrates are not very toxic, something will happen for sure. To remove the nitrate, you can do denitrification, which means nitrate is reduced to nitrite and nitrogen gas, a harmless gas that just evaporates into the air.
That process requires a carbon source, and your carbon source is biofloc and shrimp feces. You might have to add a little extra carbon if things get out of balance. Normally, you can run the system for four and a half months without adding carbon and with nitrate levels of 35 ppm, which is quite low. I’ve never had to adjust my pH, which was 7.2 at the end of the last cycle. The water quality was so good at the end of that cycle that I was able to restock immediately.
One of the great things about this system is that when you drain your tank to harvest the shrimp you still have floc in the bioreactor, so you can start a new crop almost immediately.
In my system I’m not adding sugar, so I get a combination of heterotrophic bioflocs, which convert ammonia into proteins for the shrimp, and autotrophic bacteria, which convert ammonia to nitrite and nitrate. If you’re working from one cycle to the next and dumping your water, the nitrate build up is not a problem. You might have 150 ppm of nitrate after five months, but, if you kept it going for a couple of years, it would rise to 500 ppm or higher. When nitrates get that high, something will happen and the system could crash. Even though nitrates are not very toxic, something will happen for sure. To remove the nitrate, you can do denitrification, which means nitrate is reduced to nitrite and nitrogen gas, a harmless gas that just evaporates into the air.
That process requires a carbon source, and your carbon source is biofloc and shrimp feces. You might have to add a little extra carbon if things get out of balance. Normally, you can run the system for four and a half months without adding carbon and with nitrate levels of 35 ppm, which is quite low. I’ve never had to adjust my pH, which was 7.2 at the end of the last cycle. The water quality was so good at the end of that cycle that I was able to restock immediately.
One of the great things about this system is that when you drain your tank to harvest the shrimp you still have floc in the bioreactor, so you can start a new crop almost immediately.
Information:
Eric De Muylder, CreveTec bvba, Nieuwenbos 43, 1702 Groot-Bijgaarden, Belgium (phone 32-473-721-004, email eric@crevetec.be, webpage http://www.crevetec.be).
Source: Eric De Muylder. Interview by Bob Rosenberry, Shrimp News International. Veracruz, Mexico. September 26, 2009.
From Source: www.shrimpnews.com (Free News Friday, November 13, 2009)
From The Shrimp List
Eric De Muylder
(eric.de.muylder@skynet.be): I am running an experimental growout system that’s stocked with Penaeus vannamei. I use a 40% protein diet until the juveniles reach five grams, and then I switch to 35% protein. I don’t add a source of carbon, but there are enough bio-flocs in the system to convert all the ammonia and nitrites into nitrates. I use a special reactor to concentrate these reactions. The nitrate content is quite high (>350 ppm), but my shrimp are still growing at 1.5 grams per week.
Denitrification has picked up recently, and my nitrate content has stabilized. Since the carbon supply is limited, the bio-floc biomass is not very dense, so I don’t have to spend as much on oxygen. I am using a special substrate that promotes denitrification and increases the nutritional value of the bio-flocs by protecting the small organisms in the flocs that the shrimp feed on.
Denitrification has picked up recently, and my nitrate content has stabilized. Since the carbon supply is limited, the bio-floc biomass is not very dense, so I don’t have to spend as much on oxygen. I am using a special substrate that promotes denitrification and increases the nutritional value of the bio-flocs by protecting the small organisms in the flocs that the shrimp feed on.
Information:
Eric De Muylder, CreveTec bvba, Nieuwenbos 43, 1702 Groot-Bijgaarden, Belgium (phone 32-473-721-004, email eric@crevetec.be, webpage http://www.crevetec.be).
Source: The Shrimp List (a mailing list for shrimp farmers). Somebody Out There? From: Eric De Muylder. September 5, 2008.
Source: www.shrimpnews.com (Free News Friday, September 19, 2008)
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