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Biofloc Ponds Versus Traditional Ponds

Ramon Macaraig (monmac52@yahoo.com): After 125 days of culture, we harvest 25-gram shrimp from our biofloc ponds.  We used three-200-square-meter ponds seeded at 100 postlarvae (PLs) per square meter.  The PLs had growth rates of 2.5 grams a week, survivals ranging from 56 to 65 percent and feed conversions ratios (FCRs) ranging from 1.1 to 1.4.  The floc was maintained at 10-15 cubic centimeters per liter (cc/l) after 20 minutes of settlement.  The shrimp seemed to eat less when the floc was higher than 15cc.  We hope to finish our next harvests with 30-gram animals and 20 metric tons from all three ponds.

The people we sell our shrimp to say our shrimp are paler than the shrimp they get from other farms and that their shells are thinner.  They also say the flavor and sweetness of our shrimp are superior and that soft shells are not a problem.

Listers what do think is causing the pale color and thin shells?

Daniel Gruenberg (seagardenfoods@mac.com): FCRs of 1.1 to 1.4 are normal for Penaeus vannamei.  Here in Thailand, we have achieved FCRs of 0.8 with 18-20-gram animals in large-scale, pond production, so I have never been attracted to biofloc systems, but may change my mind on that someday.  I don’t see the benefit of the extra work to manage a floc system when we can optimize plankton production and feeding in a more traditional pond system.

I think the missing components in your biofloc systems are diatoms and copepods.  They provide oxygen, remove nitrogen and supply the perfect natural food for shrimp.

The biomimicry people are moving in the right direction because they have been able to bloom copepods in large numbers.  We take a slightly different approach.  We focus on diatoms because they result in a nutritionally superior zooplankton population—and encourage a copepod bloom.

Ramon, to determine the benefit of flocs, did you run any controls at the same stocking density without flocs,?

Eric De Muylder (crevetec@gmail.com): Pale color in biofloc-cultured shrimp should be expected because of the absence or reduced quantities of algae in the water.  You can solve the paleness problem by adding carotenoids to your feed.  My shrimp are nicely colored, and they are farmed in an indoor biofloc system (without light).

I also observed thinner shells sometimes, but not always, and only with a small number of shrimp.  Could this be caused by lower pH?  Generally, biofloc systems operate at a lower pH than algae-based systems.  My pH is around pH 7.4.
 
Ramon Macaraig (monmac52@yahoo.com): Eric, we are loading up on Nannochloropsis(a genus of algae with six species) in our ponds and fertilizing with phosphates to see if we can get more color in our shrimp.  Our ponds now have 10-15 cubic centimeters of floc per liter after 20 minutes of settlement.  We will lower our salinity from 30 parts per thousand (PPT) to 25 for better algae growth.  If algae turns out to be an important component of our outdoor biofloc technology, we will lower our salinity level even more, to around 17 ppt, a level our Nannochloropsis likes better.

We had soft shells in a previous run, so we have been keeping the alkalinity higher than 150 with a daily application of calcitic lime.  The soft shells are gone, yet the shells seem thinner than usual.  It may have something to do with the shrimp’s fast growth (2.5 to 3.0 grams per week) with animals larger than 18 grams.  The pH is stable at 7.4 to 7.6 in two ponds and 7.8 to 8.0 in the third pond.

Ramon Macaraig (monmac52@yahoo.com): Daniel, my desire to try biofloc shrimp farming came after painful whitespot losses in sterile quarantine systems.  We are now looking for approaches that minimize stressful conditions caused by fluctuations in water quality.

So far we have had success using water from tilapia ponds for bioremediation.  We add five centimeters of tilapia water per hectare of shrimp pond from ponds carrying a minimum of two kilograms of tilapia biomass per cubic meter.  We have had 25 good runs and just one bad one in our 3,000-to-6,000-square-meter ponds using this system, which produces 18-gram animals and 16 to 25 metric tons per hectare from a stocking density of 100 to 150 postlarvae per hectare.

By the way, the early feeding of rotifers to the PL in this biofloc trial did not kill the shrimp as feared by pond managers who were punch drunk from whitespot disasters.  Maybe early feeding with copepods, Moina and Artemia followed up with the protocols coming out of the biomimicry concepts could open another approach for managing pond stressors in intensive shrimp culture.

Billy Setio (surijo_setio@yahoo.com): Hi Ramon, in the past, when I was working with biofloc systems, I had the following water quality parameters:

Alkalinity 180.
Salinity 32.
Best pH 7.5 to 7.8 (don’t go lower).
Dissolved oxygen in the range 3 to 3.5 ppm is okay.
Transparency 15 to 25 centimeters.
Imhoff floc density best at 6 to 8 centimeters per liter.

With the above parameters, you don’t need to culture algae; nature will provide it, and you’ll get good shell formation.  If the pH and alkalinity are any lower, you’ll get softer shells, but I’m not sure why.

At the beginning of the culture cycle, we shift the system to more algae, and at the end of the cycle, a thin density of bioflocs starts to form.  At that stage, I would say the system was 80% algae and 20% floc.  The high percentage of algae gives us better protection against white feces syndrome, which is now hitting Indonesia very hard.

Ramon Macaraig (monmac52@yahoo.com): Hello Billy, thanks for your water quality parameters.  They are good benchmarks.  We are almost at those numbers in our three ponds, except for the Imhoff cone floc density, which we targeted at 10 cc/l.  At day 85, we averaged 12-gram shrimp in two ponds; and at day 60, we averaged 7.5-gram shrimp in the other, with Secchi disk transparency at 15-20 centimeters.  We are hoping to get algae growth in the next few days to see if it will influence shell color and hardness.  I will report the results to The List after we harvest all three ponds.

Billy Setio (surijo_setio@yahoo.com): Ramon, if you drop your floc density, your shrimp should be larger than 15 grams at day-85 because you can increase the feed.

Daniel Gruenberg (seagardenfoods@mac.com): Hi Ramon, I was not aware that it was whitespot that encouraged you to try bioflocs.  After whitespot showed up in Thailand, I focused on natural food.  Any kind of natural food is superior to pellets.  There are probably nutrients in natural food that are not found in pelleted feed.

In my opinion, the whole idea of killing everything in the pond that was promoted by big companies in Asia was a massive error.  Instead, we refined our diatom fertilizers, which encouraged higher dissolved oxygen levels, while simultaneously reducing nitrogenous wastes in the pond.  Diatoms also encourage copepods, which are the main natural food of shrimp.  We got very good results, all in blissful ignorance about the PCR tests that showed copepods to be carriers of whitespot.

I have never tried rotifers, but unfortunately, I have never had a farm close enough to a hatchery where I could bloom copepods in sufficient quantity to feed my larvae.  I have been wanting to try this for a long time.  Hopefully, we can soon give it a try.

Your biomass level is very high, which is very impressive.  I’m curious, do you end up with a lot of sludge after harvesting such a high-density crop?

I am focusing on about half your stocking density and ways to improve natural food concentrations, reduce FCRs and lower costs.

Our latest strategy results in very little sludge on the bottom of the pond.

Ramon Macaraig (monmac52@yahoo.com): We have harvested the three ponds.  The thin-shell problems seems to have been corrected by increasing alkalinity to 150; however, our buyers still thought our shrimp were rather pale.  Adding Spirulina powder to the diet during the two weeks prior to harvest did not work as well as expected.  We will encourage green algae in our next run.

We harvested three ponds.  The production data is as follows:

  One    Two Three
Area (square meters) 1,200 1,200 1,300
Biomass (metric tons) 17.14 18.83 20.05
Average Body Weight (final harvest grams) 28.4 26.5 29.4
Days of Culture  141 141 145
Shrimp Per Square Meter  68 77 82
Survival Rate 52.6% 61.3% 54.6%
Feed Conversion Ratio 1.61 1.41 1.37
Estimated Maximum Biomass (metric tons) 14.5 16.4 14.7

This was the first time we made money, about $15,000 per hectare, on shrimp monoculture at this farm (Alsons Aquaculture Corporation), which in the past was hit by whitespot disasters and by disease fears, which lead to early, unprofitable harvests.

After comparing our runs with Billy Setio’s, we have more questions about biofloc farming in open ponds.

  Billy Setio Ramon Macaraig
Alkalinity (ppm)  >180 >150
Salinity (ppt) 32  35-38
Best pH Range 7.5-7.8 7.6-8.4
pH AM/PM Variance no data 0.1-0.3
Minimum Dissolved Oxygen (ppm) 3.0-3.5 3.0-3.5
Transparency (cm)  15-25 10-20
Imhoff Floc Density (ml) 6-8  10-15


To improve survival rates, would feeding postlarvae with rotifers and copepods improve survival rates?

The FCRs were relatively decent, by our standards, but feed-tray monitoring hinted that there might have been some mortality early in the cycle.  Could we use cheaper feeds or lower protein feeds because the shrimp must be feeding on some biofloc?  Our feed costs were $1.70 for each kilogram of shrimp produced.

We used six horsepower (hp) of aeration per pond, four hp from paddlewheels and two hp from blowers, which keep the bioflocs suspended in the water column.  Aeration cost $1.20 per kilogram of shrimp produced, more than double what we had budgeted.  Are paddlewheels necessary in this case?  Could we get by without blowers?

What parameters are important in aeration systems (type of aerator, orientation, time of use) in one-hectare, biofloc ponds and in two-hectare biofloc ponds?

We estimated that we used 29.5 metric tons of feed and four metric tons of molasses as a carbon source per hectare.  Yet at harvest, the sediment at the bottom is only at five centimeters near the center of the pond.  Where did all the sludge go, since we never drained any water?  We started with 1.2 meters of water and added 0.8 meters during growout.

By the way, the three ponds have no liners and no bird-scare lines.  We use tire baths and wash stands for biosecurity.

Jorge Cordoba (seabizec@yahoo.com): Ramon, what percentage of your total cost goes to feed?

Ramon Macaraig (monmac52@yahoo.com): With these trials, the direct cost structure looks like this: feeds 44%, power 31%, postlarvae 10%, floc 8% and labor 7%.

Jorge Cordoba (seabizec@yahoo.com): Thank, Ramon, appreciate your inputs.  You should be able to save some money on feed and power.  Maybe by using less protein in your feed and increasing your use of solar and wind power.
 
Billy Setio (surijo_setio@yahoo.com): Ramon, do you have capacitor banks installed on your main power line?  They reduced my power loss by 10-20%.  What’s the cost of your power per kilowatt hour (kwh)?

Ramon Macaraig (monmac52@yahoo.com): Billy, Yes we have capacitor banks installed.  Power costs $0.115/kwh in our area.  We are working on lowering aeration costs by growing more green algae and maybe cutting back on paddlewheels.

Billy Setio (surijo_setio@yahoo.com): Ramon, I think your problem is survival and growth rates, which lower your yields per hectare.  If you produce 15 tons per hectare, 30 hp per hectare of aeration should be enough.

Daniel Gruenberg (seagardenfoods@mac.com): Billy do you really think growth rate is Ramon’s problem?  He’s getting 0.2 grams per day, which is higher than average.  Could he get more?  Yes, I think he could, but anything above 0.2 grams per day at his high densities is just icing on the cake.

I really dislike paddlewheels.  I think blowers are much better.  I would run them 15 minutes on and 15 minutes off during the day and constantly at night.

Copepods are great food for shrimp, and I never had a problem with whitespot when I used them.

Swings of 0.3 pH units a day stresses shrimp.  I would try to increase alkalinity a bit more to stabilize pH.

More blowers and fewer paddlewheels would also help.

What was your feed cost and FCR?

Great work and best of luck on your next run.

Billy Setio (surijo_setio@yahoo.com): Hi Daniel, feed costs are 50% of my total cost of goods sold.  My average FCR is 1.2 for producing 22-gram shrimp in a 90-day production cycle, with survivals around 80-90%.  Overall my total cost of goods sold is less than three dollars a kilogram.  I always shoot for a weekly gain of 2 to 2.5 grams a week.  At an average stocking density of 135 postlarvae per square meter, I can produce 22 metric tons per hectare.  At 90% survival, I would get 25 tons per hectare.  If I extended the growout period to 98 days, I would produce 27 tons per hectare.

In Ramon’s case, survival is too low and power costs are too high.

My aim is to have around 5.5-gram shrimp at six weeks and 19-21-gram shrimp at 13 weeks, with a feed conversion ratio of 1.1 to 1.3.

I create a circular current in my ponds to concentrate the sludge in the center of the pond and then siphon the sludge away once a week.  I prefer brown-algae color to green-algae color because it produces better growth.

Ramon Macaraig (monmac52@yahoo.com): Billy, Thanks for the numbers.  You are spot on for the priorities on my next crop.  I plan to aggressively feed my postlarvae in a separate enclosure and supplement their feeds with rotifers and copepods.  I also plan to develop the floc in the growout ponds as early as possible, an improvement over my last run when we had 10 ml of floc at 12 grams.  I am sure this will improve survival rates and growth.  I hope to get to your 22 grams in 90 days.

We will grow green algae early to get good shrimp color as Eric suggested.  Nannochloropsis culture is available and is part of our milkfish production system.

Then we can thin out more by using a carrying capacity ceiling of 16 metric tons per hectare and push for bigger sizes as the selling price structure in our area is $0.103 per gram beyond 10 grams.  We create a lot of value if we can still get at 2.5 to 3.0 grams a week at that stage.

Ramon Macaraig (monmac52@yahoo.com): Daniel, Thanks for the insights.

Yes, we recognize the early slow growth problem, coupled with the survival rate of 60% from seeding 130-140 postlarvae per square meter, which points to feed shortages in the postlarvae and juvenile shrimp.  We will concentrate them at 1,000 per square meter in a nursery pond and feed them aggressively with feed mash, rotifers and copepods.

We will cut down on paddlewheels and will only use them to circulate water at night.  If we grow more green algae, it should absorb the early morning ammonia from the feces and the feeds, producing a bloom around noon along with more oxygen that will support biofloc formation.  The blowers will suspend the bottom muck, which should be oxidized by the oxygen produced from algal photosynthesis.  That will be a good time to apply molasses to adjust the carbon:nitrogen ratio.  At 16 metric tons of shrimp biomass, feeding at 1.5% of biomass, 10 kilograms of unwanted ammonia-N is supplied per hectare per day that needs to be deactivated.

We will increase our alkalinity to Billy’s 180 ppm to minimize the days when the morning and afternoon pH vary a lot.

We are now more confident about scaling up our operations to one-hectare earthen ponds.

Eric De Mulyder (eric@crevetec.be): Hello Ramon, Do you have ammonia problems?  What was your reason for using molasses?  If you can cut back on your molasses, you will also cut your electricity cost for aeration and might get higher oxygen levels in your ponds.

Ramon Macaraig (monmac52@yahoo.com): Eric, ammonia is always a problem in intensive shrimp ponds fed with formulated feeds.  The recirculating aquaculture people are removing it with protein skimmers—right?  That’s the reason why we are simplifying the culture system by not changing water and applying carbon with molasses.  Dallas is always reminding The Shrimp List of Steve Serfling’s ODAS and Yoram Avnimelech’s discussions on biofloc as a scrubber for ammonia through bacterial action.  The nutritional benefits are just a bonus.  If we get stable water quality, survival and growth will follow, and then we’ll take a look at how we might save on feed costs by taking advantage of the nutrition in the biofloc.

Eric De Muylder(crevetec@gmail.com): Hello Ramon, since you don’t change water, you can allow nitrifying bacteria to develop, which will convert ammonia into nitrite and nitrate.  This is much less costly, since you save on molasses and electricity.  I only use additional carbon in my nursery and sometimes in my pre-growout ponds, where the amount of feed increases daily.  Once the shrimp reach five grams, I don’t need to add carbon anymore because the amount of feed per day stabilizes and the nitrifying bacteria absorb the excess nitrogen.

Mark Rigby (mrigby@llyn-aquaculture.co.uk): Having reared shrimp at over eight kilograms per cubic meter (over 10 kg per m2), I agree with Eric that there is no need to add additional carbon as long as there is sufficient carbon in the feed.  At that stage pH, O2, alkalinity and suspended solids management become the most important factors.  I forget who mentioned soft shells, but they are definitely a result of low pH.

Ramon Macaraig (monmac52@yahoo.com): Mark, if your biomass was eight kilograms per cubic meter, you must have been feeding 150 grams of feed, 60 grams of protein and 10 grams of nitrogen per square meter.  If what is retained is eight grams of total ammonia nitrogen and 75 grams of carbon in the water, you are almost at a C/N ratio of 10.  In our case of 1.6 kilograms per square meter, the C/N ratio must be about the same.  As suggested by Eric, in one of our next runs, we will try to detect, monitor and maintain the nitrifying bacteria in our ponds.

Sources: 1. The Shrimp List (a mailing list for shrimp farmers).  Subject: Biofloc Questions.  March 1 to October 26, 2016.  2. Bob Rosenberry, Shrimp News International, November 6, 2016.

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