International Journal of Recirculating Aquaculture

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https://hdl.handle.net/10919/106558

A peer-reviewed journal dedicated to the consolidation of research and applications expertise in the area of recirculation systems, 2000-2017.

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Two organic carbon application rates to control inorganic nitrogen in minimal water exchange, biofloc, shallow water, shrimp nursery systems
Crockett, Jack; Lawrence, Addison (Virginia Tech Publishing, 2017-09-01)
The objectives of this study were to develop and test a quantitative method for reactive carbon application to control inorganic nitrogen, and to compare the effect of carbon application using 40% and 60% microbial conversion efficiency (MCE) while leaving a residual 11.3 mg/l nitrate nitrogen (NO3-N) level. The organic carbon requirement was based on the carbon to nitrogen ratio of the elemental composition of microbial cells. The source of supplemental organic carbon was shortchained fructooligosaccharide (scFOS). Correction for moisture was duplicated on the first 2 days of scFOS application, so the actual efficiency rates were 35.1% and 58.3%. The proposed carbon quantitative method was effective in predicting the amount of carbon required to control inorganic nitrogen. Both 35.1% MCE and 58.3% MCE maintained total ammonia nitrogen (TAN) and nitrite nitrogen (NO2-N) at desired levels of equal to or less than 2.3 mg/l and 3.1 mg/l, respectively. The amount of carbon applied using 35.1% MCE was higher than with 58.3% MCE. e 58.3% MCE treatment resulted in slightly higher NO3-N levels than 35.1 % MCE. The most toxic species of inorganic nitrogen, TAN and NO2-N, are assimilated by heterotrophic bacteria before NO3-N, permitting decreased reactive carbon input and water quality improvement. The benefits of 58.3% MCE vs. 35.1% MCE were lower organic loading, reduced water replacement, and decreased costs. The total water replacement associated with biofloc control was 0.24% using 35.1% MCE and 0% using 58.3% MCE. After a culture period of 14 days the mean weight was 65.5 mg and 61.9 mg for 31.5% MCE and 58.1% MCE, respectively, and a survival of 79.5% for both MCE’s.
Hematology and Serum Chemistry Values for Winter Flounder (Pleuronectes americanus)
Dye, V. A.; Hrubec, T. C.; Dunn, J. L.; Smith, Stephen A. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
Clinical analysis of blood to determine hematology and plasma biochemistry values is routinely used to assess the health of wild and domestic animals. Flounder culture is a fast growing segment of the U.S. aquaculture industry and tools are needed to monitor the health of these fish. This paper reports a complete hematologic and blood biochemistry profile for normal healthy winter flounder, Pleuronectes americanus, maintained in recirculated artificial seawater. The following hematologic values were determined: Packed cell volume, plasma protein, erythrocyte number, hemoglobin, mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, and leukocyte, lymphocyte, neutrophil, monocyte, and thrombocyte numbers. A description of leukocyte morphology is presented. Additionally, the following serum biochemical values were determined: Total protein, albumin, globulin, sodium, potassium, chloride, calcium, phosphorus, magnesium, glucose, blood urea nitrogen, creatinine, total bilirubin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, cholesterol and triglycerides. Analysis of blood parameters can enhance flounder culture by providing a means for the early detection and identification of infectious disease and of sub-lethal conditions affecting production performance.
Growth and Production Characteristics of Palmetto Bass (Morone saxatilis female x Morone chrysops male) Reared at Three Densities in a Pilot-scale Recirculating Aquaculture System
Brazil, B. L.; Nunley, Chad E.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
Production characteristics of palmetto bass (Morone saxatilis female x Morone chrysops male) reared at three stocking densities (36 fish/m3, 72 fish/m3, and 144 fish/m3) in a pilot-scale RAS were evaluated. A final mean ±SE fish weight of 412.1 ± 7.8 g at the high density was significantly lower than that of fish at the medium density weighing 542.1 ± 11 .8 g (P < 0.05). Fish weight (676.1 ± 17 .0 g) at_ the lowest density was significantly higher than at the high and medium densities (P < 0.05). The average daily weight gain at the low density (2.8 g/d) was 22% and 47% higher than fish reared at the medium and high densities, respectively. Total biomass gains of 733.8, 483.3, and 297.9 kg were obtafued at the high, medium, and low densities. Feed conversion and survival rates were similar among densities averaging 1.4 and 97 .1 %, respectively. Higher mean daily and cumulative feed totals at the highest density contributed to significantly higher ammonia and nitrite concentrations and lower pH levels at haryest. All other measured water quality parameters were similar among densities and remained within known acceptable limits for fish growth. The results indicated that palmetto bass reared in closed systems reached market size in 224 days at the low and medium densities. However, the relative biomass production may not justify such strategies when compared to the yield obtained at the highest rearing density.
Effects of water exchange and reducing dietary vitamin and mineral supplementation on survival and growth of Litopenaeus vannamei
Wang, Lan-mei; Lawrence, Addison L.; Castille, Frank; Zhao, Yun-long (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
A growth trial was conducted with Litopenaeus vannamei to evaluate effects of dietary vitamin and mineral supplementation (VMS) and water exchange on survival, growth and water quality. Four levels (0, 25, 50 and 100%) of VMS were evaluated using a 20% protein base diet. Postlarvae weighing 0.22 g were stocked for 26 days with either zero or high (5440% daily) water exchange. Growth was greater at zero than high exchange. However, growth was not affected by the level of VMS at both high and zero exchange. Survival for 0% VMS was lower than survivals for 25 to 100% VMS at high exchange. For 0% VMS, survival at high exchange was lower than survival at zero exchange. Results suggested that at zero water exchange, diets without VMS can replace diets with VMS without reducing survival.
Effects of dietary protein and water exchange on water quality, survival and growth of postlarvae and juvenile Litopenaeus vannamei
Wang, Lan-mei; Lawrence, Addison L.; Castille, Frank; Zhao, Yun-long (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
Two growth trials were conducted with Litopenaeus vannamei to evaluate effects of dietary protein and water exchange on survival, growth and water quality. In both trials, protein levels were 12, 15, 20, 26 and 35%. In the first trial, 6.21 g juvenile shrimp were stocked for 23 days at either zero or high (2750% daily) water exchange. At high exchange, survival was greater than 93% for all protein levels. Final body weight (FBW) and weight gain (WG) increased with protein level from 12% to 20% (P < 0.05). FBW and WG at 20 and 26% protein were lower than that at 35% protein. At zero exchange, survival decreased with protein above 20%. At zero exchange, water quality decreased (high ammonia, nitrite, nitrate and low pH, alkalinity) with protein greater than 15%. WG with 12% protein was greater at zero exchange than at high exchange. In the second trial, 0.22 g postlarvae were stocked for 26 days at either zero or high (5440% daily) water exchange. At high exchange, survival was 90% or greater for all protein levels. FBW and WG increased with protein level from 12% to 20% (P < 0.05). At zero exchange, FBW and WG were maximum with 20% protein. Survival was lowest at 35% protein. For 35% protein, survival was lower at zero than at high exchange. For all protein levels except 35%, WG was higher at zero than at high exchange. The results suggest that lower protein diets can replace high protein (35%) commercial diets and obtain high growth rate for both juvenile and postlarvae L. vannamei at zero exchange. Further, a 20% protein diet, which contained 25.3% marine animal meals, was adequate for shrimp growth, survival and water quality at zero exchange.
Feed efficiency of Rainbow trout (Onchorynchus mykiss) kept at high and low stocking density
Rauw, W. M.; Larran, A. M.; Garcia-Cortes, L. A.; Rodriguez, M. L.; Fernandez, J.; Pinedo, J.; Villarroel, M.; Toro, M. A.; Tomas Almenar, C.; Gomez-Raya, L. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
Feed efficiency is a trait of high economic importance in fish production, and is highly related to feeding regimes employed and stocking density. However, feed efficiency is difficult to estimate because measurements of individual feed intake are generally not available in fish that are usually reared in groups in tanks. An alternative is to estimate feed efficiency using tank as the unit of measurement. The objective of this study was to investigate tank residual feed intake in rainbow trout kept at high (HD) and low (LD) stocking density during 42 days (Day 0-14 and Day 14-42) and the consequences of subsequently reducing density in the HD treatment between 42 and 78 days (Day 42-61 and Day 61-78). HD fish weighed less at all times than LD fish (P < 0.05). LD fish grew faster than HD fish (P < 0.05) but not between Day 42-61. The coefficient of variation of body weight was larger in HD fish than in LD fish (P < 0.05) at Day 14 and Day 42. LD fish ate more than HD fish between Day 14-78 (P < 0.01). HD fish were less food efficient than LD fish between Day 0-14 but more food efficient between Day 42-61. A higher coefficient of variation of body weight in the HD tanks suggests that growth and feed intake were inhibited because of dominance relationships at a high stocking density and possibly competition for food. After relocating HD fish to a low density treatment, HD fish showed compensatory growth and compensatory feed efficiency. Although it is not practical to estimate residual feed intake individually in fish, this research shows that calculation of tank residual feed intake can be used as an alternative, especially when used to compare families for family trait selection.
Availability of Dietary Zinc Sources and Effects on Performance of Pacific White Shrimp Litopenaeus vannamei(Boone)
Bharadwaj, Anant S.; Patnaik, Susmita; Browdy, Craig L.; Lawrence, Addison L. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
A study was conducted to evaluate the response of Pacific white shrimp Litopenaeus vannamei to inorganic or chelated sources of dietary zinc. Two sets of diets, one supplemented with zinc from zinc sulfate (55, 80, 116, 168, 243 and 363 ppm zinc) and the other with zinc from a chelated source (methionine hydroxy analog chelate; 39, 52, 65, 78 and 104 ppm zinc) were fed to replicate groups of juvenile shrimp (N = 8; 0.4 g initial weight) for 6 wk. All experimental diets contained 1.38% phytic acid reflecting levels in typical commercial feeds. Final weight, growth rate and biomass of shrimp fed zinc sulfate supplemented diets (243 and 363 ppm total zinc) were significantly higher (p < 0.05) than that in shrimp fed the base diet. In contrast, performance of shrimp fed the chelated source of zinc was significantly higher than shrimp in the control group at much lower levels of supplementation (65 and 78 ppm total zinc). Results indicate that shrimp required 3-4 times more dietary zinc from zinc sulfate than zinc from a chelated source to promote comparable growth when fed diets containing phytic acid. The chelate tested proved to be a safe, effective and available source of zinc for the Pacific white shrimp.
Comparison of Growth, Feed Conversion and Survival of Morone saxatilis female x M. mississippiensis male and M. saxatilis female x M. chrysops male Hybrids Reared in Recirculating Aquaculture Systems
Bosworth, B. G.; Libey, George S.; Wolters, W. R. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
Striped bass female (M. saxatilis) x white bass male (M. mississippiensis), (SBxWB, n = 300) and striped bass female x yellow bass male (M. chrysops) (SBxYB, n = 300) fingerlings, initial mean weight 91 g and 62 g, respectively, were reared in recirculating aquaculture systems at densities of 118 fish/m3 for 120 days. Mean weight increased 309 g and 151 gin SBxWB and SBxYB, respectively. ,final mean weight and total length, and rate of weight and length increase were higher for SBxWB than SBxYB. Condition factor and survival were higher for SBxYB (1.04 and 99.3%, respectively) than for SBxWB (1.01 and 96.0%,respectively). Mean feed conversion ratio (FCR) was lower for SBxWB (1.4) than for SBxYB (1.6). Significant time x hybrid interactions indicated that growth rate of SBxYB improved, relative to SBxWB, as the study progressed. Positive linear trends for total ammonia, unionized ammonia, and nitrite indicate water quality deteriorated as the study progressed. Time x hybrid interactions for growth rate may have been due to differential responses of SBxYB and SBxWB to deterioration of water quality. Although SBxYB had slightly better survival than SBxWB and their growth rate improved relative to that of SBxWB, the slow overall growth of SBxYB limits its potential for recirculating system production.
International Journal of Recirculating Aquaculture, Volume 12 Complete Issue
(Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
The International Journal of Recirculating Aquaculture presents research and applications expertise in the area of recirculation systems and technology. This journal is intended to be a forum for the open exchange of reliable information on the subjects of recirculating aquaculture. The industry of recirculating aquaculture requires expertise from many different fields such as animal husbandry, economics, water chemistry, waste managment, food safety, genetics, and systems engineering. The following papers focus on a variety of topics, with recirculation as the common element.
The Effect of Solids Removal on Water Quality, Growth and Survival of Litopenaeus vannamei in a Biofloc Technology Culture System
Gaona, C. A. P.; Poersch, L. H.; Krummenauer, D.; Foes, G. K.; Wasielesky, W. J. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
Biofloc technology culture systems can increase the productivity of shrimp culture. Through the use of minimal or zero exchange, biofloc technology culture systems can also reduce the use of water. Diet enhancement through the addition of feed increases the amount of excreta. Together with unconsumed feed, the additional excreta increases the amount of suspended solids and reduces the concentration of dissolved oxygen. In addition, the excess of suspended solids can harm the culture by reducing light penetration. In turn, the lower light levels reduce the abundance of photosynthetic organisms (microalgae) that are also important for water quality and shrimp nutrition. The objective of this study was to evaluate the removal of suspended solids from the water of the culture system by a clarification process (i.e. particle settling). Two treatments were applied: with clarification and no clarification. Six tanks, each 35 m³, were used in the study. In the clarification treatment, 35 m³ of water with bioflocs was pumped from the experimental unit for 6 hours. The water passed through a settling tank (1,000 L) and was returned to the culture unit through gravity. The clarification treatment reduced total suspended solids (24.5%), turbidity (27%) and chlorophyll a (27.8%). The availability of dissolved oxygen and pH values were also greater in the clarification treatment. Growth, feed conversion ratio, survival and productivity were significantly higher (p<0.05) with the removal of suspended solids. Control of the concentration of suspended solids contributed to the improvement of water quality and the growth performance of the shrimp L. vannamei in the superintensive biofloc technology culture.
Book Review: Recirculating Aquaculture, 2nd Ed. by M.B. Timmons and J.M. Ebeling
Hall, Steven G. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
Effect of a Parabolic Screen Filter on Water Quality and Production of Nile Tilapia (Oreochromis niloticus) and Water Spinach (Ipomoea aquatica) in a Recirculating Raft Aquaponic System
Danaher, Jason J.; Shultz, Charlie R.; Rakocy, James E.; Bailey, Donald S.; Knight, Lasiba (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
Aquaponics is an integrated fish and plant recirculating production system. Solid fish waste must be removed from the production system to maintain optimal water quality parameters for fish and plant health. The University of the Virgin Islands (UVI) raft aquaponic system’s primary treatment device for solids removal is a cylindro-conical clarifier; however, alternative mechanical filtration devices such as a parabolic screen filter (PSF) may offer advantages. The objectives of the elevenweek experiment were to compare water quality parameters, Nile tilapia (Oreochromis niloticus) production and water spinach (Ipomoea aquatica) production in a raft aquaponic system using either a cylindroconical clarifier or parabolic screen filter for primary treatment of solids in the waste stream. The water quality results showed no significant differences (P > 0.05) between treatments for temperature, oxygen, pH, alkalinity, EC, TAN, NO2-N and NO3-N, macronutrients and micronutrients concentrations, with the exception of copper and zinc. There was no significant difference (P > 0.05) between treatments for the total suspended solids (TSS) concentration entering either primary filtration device; however, there was a significant difference (P ≤ 0.05) between treatments for TSS concentrations exiting the primary filtration device. The PSF treatment had a significantly higher (P ≤ 0.05) TSS concentration exiting the unit and a significantly higher (P ≤ 0.05) TSS concentration in the secondary treatment device (net tank) compared to the clarifier. There were no significant differences (P > 0.05) between treatments for Nile tilapia production, average weight, survival, or feed conversion ratio. There were no significant differences (P > 0.05) in water spinach production or plant tissue analysis between treatments. In conclusion, the PSF used in this experiment performed less effectively in removing TSS compared to the clarifier, would require more labor to clean and would not be recommended for use in a larger raft aquaponic system. In addition, water spinach assimilated dissolved fish wastes well and grew vigorously in the raft aquaponic system.
Water Quality and Nutrient Aspects in Recirculating Aquaponic Production of the Freshwater Prawn, Macrobrachium rosenbergii and the Lettuce, Lactuca sativa
Khoda Bakhsh, H.; Chopin, T. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
The purpose of this study was to investigate the effects of different nutrients and their ability to improve the production of Macrobrachium rosenbergii and Lactuca sativa in a prototype recirculating aquaponic (RA) system. Experimental units were set up with different amounts of supplemented organic and inorganic (complex minerals) nutrients to carry out the study. The results indicated that desirable growth of M. rosenbergii might be possible in RA systems when supplied sufficient levels of macro-micro nutrients. Analyses of nutrients in the prawn culture tanks demonstrated that ammonia and nitrate concentrations were critical in maintaining proper water quality during the culture period. Five-day biological oxygen demand (BOD5) increased significantly with the increased loading of organic supplement in the rearing tanks. A significant linear relationship of chlorophyll a and N:P ratio was observed among the treatments. The combination of complex minerals and organic chicken manure (CM15) displayed a higher N:P ratio, maximal total yield and did not show adverse effects of NH3 concentrations and other important water quality parameters.
Select Hematological Values of the African Catfish (Clarias gariepinus) Raised in a Water Recirculating Aquaculture System
Akinrotimi, O. A.; Bekibele, D. O.; Orokotan, O. O. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2011-06-01)
Clinical evaluation of blood parameters is routinely used to assess the health of wild and domestic animals. The commercial catfish industry in Nigeria has undergone rapid expansion in recent years. An understanding of normal hematology values for healthy fish and the identification of predictors of the onset of health problems may enable fish health specialists to intervene before major losses occur. This paper reports values for selected hematological parameters of normal healthy African catfish (Clarias gariepinus) (n=120) raised in a recirculating aquaculture water recirculation system, including hemoglobin (Hb), red blood cells (RBC), packed cell volume (PCV), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), thrombocyte count, and leukocyte differential (lymphocytes, neutrophils and monocytes). Significant differences (p< 0.05) were observed between males and females in the values of Hb, PCV, and thrombocytes. This work provides hematological baselines for selected values for Clarias gariepinus in recirculation systems, and is intended to enhance production performance through early detection and identification of infectious diseases.
International Journal of Recirculating Aquaculture, Volume 11 Complete Issue
(Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2010-06-01)
The International Journal of Recirculating Aquaculture presents research and applications expertise in the area of recirculation systems and technology. This journal is intended to be a forum for the open exchange of reliable information on the subjects of recirculating aquaculture. The industry of recirculating aquaculture requires expertise from many different fields such as animal husbandry, economics, water chemistry, waste managment, food safety, genetics, and systems engineering. The following papers focus on a variety of topics, with recirculation as the common element.
Book Review - Species and System Selection for Sustainable Aquaculture
Schwarz, Michael H. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2010-06-01)
Water Quality in Identical Recirculating Systems Managed by Different Aquaculturists
Hanna, K.; Wheaton, F.; Lazur, A.; VanKeuren, S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2010-06-01)
Water quality in recirculating aquaculture systems is a function of many variables including system design, loading, and management; temperature; feeding rate, and other variables. This research attempted to determine how different managers’ management practices affected system water quality when the managers were using identical production systems. Water quality was monitored in two tanks on each of three farms, and an attempt was made to correlate management practices with the resulting tank water quality. The investigators worked with farm managers to collect as much data as possible about the management practices of each manager, economic data, when fish were placed into the tanks and when they were harvested, growth rates and other information. The resulting analysis proved there is great variation in water quality parameters in individual tanks both between farms and within a farm. The study showed that management of aquaculture systems had a strong influence on tank water quality. Operational data on economics, filter cleanings, fish growth and other information proved to be difficult to obtain as the managers did not keep detailed records of many of these variables. As a result, it was not possible to relate water quality to economics of the farm. It was apparent that good records are necessary for an aquaculture production facility if the operation is to be successful.
Production of Microbial Flocs Using Laboratoryscale Sequencing Batch Reactors and Tilapia Wastewater
Kuhn, D. D.; Boardman, Gregory D.; Flick, George J. Jr. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2010-06-01)
Laboratory-scale studies using sequencing batch reactors (SBRs) were conducted to evaluate microbial floc production and treatability of fish effluent from a tilapia farm utilizing recirculating aquaculture systems (RAS). Several trials were conducted, both with and without carbon sucrose supplementation. Results from this project suggest that treatment with carbon supplementation improved nutrient removal from the fish effluent and increased microbial floc production. Successful treatment of effluent using bioreactors could accomplish two primary objectives. The first objective is improving water quality of effluent to maximize water reuse. Secondly, production of microbial flocs is a means of recycling nutrients from the effluent into a useable and alternative protein source for aquaculture diets. Ultimately, this option could offer a sustainable option for the aquaculture industry.
An Overview of Design Considerations for Small Recirculating Fish Culture Systems
Harmon, T. S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
Aquatic system engineering is an important factor when designing a new fish holding system or renovating an existing system. Indoor recirculating aquatic systems may be used for various operations, some of which may include: the quarantine of new animals, isolation for ill fish, aquaculture, research, or as educational displays. Professional engineers generally design large or high-density systems using a massbalance approach. However, smaller systems are typically designed or renovated by their immediate owners, which may include aquaculturalists, aquarists, biologists, zoologists, or professors. In many instances trial and error is used to size the equipment, which can get very expensive and take up valuable time. Undersized or oversized equipment wastes electricity and possibly reduces the life of the equipment. These limitations can be avoided by using the practical guidelines given here and taking into consideration a few simple design factors. Proper design of these systems can be accomplished by much quicker methods than a full-scale mass-balance approach and will typically work for low-density systems.
Use of Coral Rubble, Aquamat™ and Aquaponic Biofiltration in the Recirculating System of a Marine Fish Hatchery
Estim, A.; Mustafa, S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2010-06-01)
A preliminary study on the effect of combination biofilters, including coral rubble, geotextile Aquamat™ (Meridian Aquatic Technology, Silver Spring, MD, USA), and algal aquaponics in a marine fish recirculating system was investigated. Aquamat™ is an innovative product fabricated from highly specialized synthetic polymer substrates. Aquamat™ forms a complex three-dimensional structure that resembles seagrass in appearance, and has been used to support high stocking densities in fish culture ponds and enhance biological processes. In addition, coral rubble was used, and two seaweed species, Eucheuma spinosum and E. cottonii, were evaluated for their usefulness as aquaponic biofilters in a recirculating system. Results showed that the four different biofilters operating within the recirculating system were significantly different (P<0.05) in NH3-N and NO3-N concentrations. The lowest mean NH3-N concentration was recorded in the recirculating tank using Aquamat™ + seaweed + coral rubble, while the highest mean NO3-N concentration was recorded in the recirculating tank using Aquamat™ + coral rubble. Fish weight gain and survival rates were not significantly different (p<0.05) in the four recirculating systems. In the second experiment, three varieties of Eucheuma spp. grew poorly, and produced no noticeable effects on NH3-N, NO2-N and NO3-N concentrations. Eucheuma cottonii decayed in the early days, while the two varieties of E. spinosum decayed after 35 days. Once decayed, water quality impairment followed. This study concluded that Eucheuma species were not suitable as a method of biofiltration in a recirculating culture system. While these seaweeds do remediate water quality, they themselves require a good environment to perform this role. When conditions are not optimal for the stocked organisms, the co-culture system can produce negative results. Followup investigation is needed to determine the suitability of such integrated aquatic systems for a large-scale fish production in recirculation systems.

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