Evaluation of water quality, growth performance, feed efficiency and survival of Labeo rohita (Rohu) and Carassius auratus (Gold fish) in a recirculating aquaponics system

Introduction

Rapid growth in the human population has created numerous environmental challenges, including water scarcity, degradation of arable land, rapid climate change, and land salinization (Dijkgraaf et al., 2019; Goddek et al., 2019a; Yang and Kim, 2020) [3,8,29] . To eliminate the disparity between available resources and expanding demand for food, there is a need to change from a growth-dependent, cost-effective model to one that prioritizes environmentally friendly food production systems in a balanced manner, assuring nutritional security (Goddek et al., 2019a) [8] . Pisciculture as a rapidly expanding sector, offers a viable solution to achieve both food security and the growth of entrepreneurship. However, traditional aquaculture technologies such as ponds and open-water systems pose significant environmental problems, including eutrophication and habitat degradation. Therefore, addressing these problems requires implementing a more intensive, cost-effective, and ecologically friendly food production approach (Dijkgraaf et al., 2019) [3] As a zero water exchange technology, aquaponics offers a potential solution by improving the recycling of nutrients and culture water, hence reducing the negative discharge from aquaculture sites. This system has a 95-99% water reuse rate and effectively uses scarce land and water resources. Furthermore, it offers numerous financial advantages through the sustainable production of plants and fish (Nuwansi et al., 2015) [18] . Aquaponics represents a biologically-integrated model which improves the availability of nutritious foods, aligns with United Nations Sustainable Development Goals (Goal 2: Zero Hunger and Goal 14: Life Below Water), and fulfils the needs of a growing global population (Goddek et al., 2019a; Ani et al., 2022) [8] . The technique combines recirculating aquaculture and hydroponics, using nutrient-rich culture water effluent from fish tanks with waste and uneaten feed as the principal fertilizer supply for plants. Filtered water is recirculated to fish tanks. Aquaponics reduces the need for nutrient supplementation in hydroponics and improves waste-water purification in the RAS. This results in excess nutrient exclusion and increased profitability by producing two marketable crops concurrently (Hu et al., 2015; Nuwansi et al., 2015) [13,18] . The primary aim of this study was to determine the growth performance of food fish and ornamental fish with selected horticultural plants in an aquaponics system. furthermore, it also demonstrates the potential of aquaponics as a sustainable strategy for integrating aquaculture and horticulture to increase production.

Materials and Methods

Experimental Site

The present research work was carried out at the polyhouse of the College of Fisheries Science (COF), Kamdhenu University at Rajpur (Nava) Himmatnagar.

Experimental Fish

The healthy and non-infected advance fry of Labeo rohita and Carassius auratus (Family: Cyprinidae and order: Cypriniformes) were used for in vivo experiment. The stock of fish was obtained from the State Fisheries Department-Ukai, Gujarat. The average weight of the rohu fish (1.36±0.026) g and gold fish was (1.34±0.02) g. The prophylactic treatment following the standard protocol of bath treatment in 0.05% potassium permanganate solution was given to fish before placing them in an acclimatization tank. Fish was reared one month under laboratory conditions for proper acclimatization under the optimal condition, before taking them for in-vivo experiment. Commercial feed was used to feed the fish.

Experimental design

The experiment was carried out in pretreated (2ppm KMNO4, fully washed 3-4 times and sun dried) 1000 Liter capacity circular FRP tanks and filled with pre-quality tested borewell water in each circular tank. The experimental design was CRD, and the tanks were set up in triplicates for treatment and control group. The experimental fish Labeo rohita (Rohu) and Carassius auratus (Gold fish) were stocked at a rate of 1gm/l of water. After acclimatization period, fish fry with an average initial body weight of rohu (1.36±0.026) g and (1.34±0.02) g of gold fish were randomly distributed in replications. 10-15% Water refilled to compensate the evaporation loss. The fish fry were fed at the rate of 10% of body weight in split dosed twice a day for first 30 days and 8% for subsequent time. Growth parameters of fishes and plants were monitored fortnightly. The experiment lasted for 60 days.

Preparation of Aquaponics System

The aquaponic system has been expanded with recirculation in two sections. The Floating Raft Aquaponic System was created utilizing thermocol sheets. To create the floating raft, we used thermocol sheets that were 1 meter long, 0.5 meter wide, and 0.03 meter thick. The aquaponic structure consisted of six thermocol sheets with implanted plant seeds. Six sets of Floating Raft Aquaponic Systems were set up, with seedlings securely fixed in 2-inch diameter planting pots and placed 6 inches apart on floating sheets. Each floating raft could hold 16 seedlings from four distinct plant varieties. The second phase was to construct the aquaponic system's media bed, which included four crates for each replicate, resulting a total of 12 crates over three replication units. The rectangular plastic crates had a capacity of 160 liters and measures 0.77 meters in length, 0.53 meters in width, and 0.40 meters in depth. The crates were pre-filled with pebbles of various sizes to provide a homogeneous media bed thickness of 11.3 cm meters. Plant seedlings were then placed on top of the medium bed. The media bed aquaponic assembly was placed after the main tanks and goldfish tank in a duplicate configuration, while the floating bed aquaponics assembly floated on the FRP (rohu and goldfish tanks, respectively).

Water quality parameters

Water quality parameters such as temperature, pH, TDS and electrical conductivity were determined in the biochemistry lab by HANA multiparameter bench meter (HI 5522, USA).

Growth parameters of experimental fish

Growth parameters such as Percentage Weight Gain (gm), Specific Growth Rate (SGR), Feed Conversion Ratio (FCR), Protein Efficiency Ratio (PER) and Lipid Efficiency Ratio (LER) were calculated. The growth performance assessed at 15 days intervals by randomly sampling 15 fish from each tank in all experimental replicates.

Statistical Analysis

The results of the present study were statistically analysed using completely randomized design (CRD) and one-way analysis (ANOVA) using IBM® SPSS® version 26.00 software and significant differences (p<0.05) among treatment means were compared using Duncan multiple range test (DMRT).

Results and Discussion

Water quality parameters

The water quality parameters observed during the experimental period are presented in Table 1. The water temperature ranged from 27.72±0.09 °C to 29.90±0.00 °C, while the pH ranged from 7.93±0.08 to 8.64±0.15, which is ideal for fish, plants, and nitrifying bacteria growth. The optimal pH range for nitrification is 7.0 to 9.0 (Chen et al., 2006) [2] . Medina et al. (2016) [16] reported 8.3 pH in a recirculating aquaponics system. The obtained result of present study were well within the optimal range and in agreement with the findings of Santhosh and Singh (2007) [23] and Chen et al. (2006) [2] . The electrical conductivity measured in this study varied from 900 to 925 µS cm⁻¹ in the control and 873 to 934 µS cm⁻¹ in the aquaponics system.

Stone and Thomforde (2004) [26] state that water with an electrical conductivity between 100 and 2000 µS cm⁻¹ is preferred and suitable for fish culture. According to FAO (2014) [7] and Grabet and Junge (2009) [10] , these values are well within the suggested EC range for aquaponics systems (300-1100 µS cm⁻¹), which is considered optimal for maintaining nutrient availability for plants while preventing osmotic stress in fish. The total dissolved solid concentration in this investigation ranged from 511.33±19.09 to 572.96±26.24 mg/l. The observed TDS values are within the recommended limits for aquaponics systems (300-800 mg/l) which is considered for adequate nutrient availability for plants while maintaining osmotic balance and fish health (Rahman et al., 2015; Rajkumar et al. 2018) [20,21] .

Growth performance of Labeo rohita and Carassius auratus

This experiment was conducted to determine the influence of a recirculating aquaponics system on the growth and survival of Labeo rohita and goldfish fry over a 60-day period. The findings of growth metrics, including mean weight increase and specific growth rate, are shown in the [22] and Goddek et al., (2019) [8] revealing higher weight gain of rohu and Gold fish reared in aquaponics system. Improved water quality through efficient nutrient removal may be the reason for higher growth in aquaponic systems, lowering physiological stress and increasing feed conversion ratio (Rakocy et al., 2006; Endut et al., 2010) [22] . Furthermore, continuous water recirculation ensures consistent nutrition supply and maintains steady physicochemical conditions that support optimal metabolic activity and fish growth performance. The SGR of Rohu varied from 1.04±0.13 to 2.64±0.21 in control and from 1.40±0.08 to 2.04±0.21 in treatment, whereas gold fish ranged from 1.35±0.28 to 4.21±0.16 and 1.16±0.02 to 3.31±0.04 in control and treatment, respectively. Hazarika et al. (2023a) [11] discovered comparable SGR in rohu in a recirculating aquaculture system. Ujjania et al. (2023) [28] found 1.37 SGR in Labeo rohita in an aquaponics system, emphasizing the need of nutrient recycling and steady water quality for fish growth.

Feed Utilization

This experiment was conducted to determine the feed conversion efficiency under a recirculating aquaponics system by assessing the utilization of feed and its conversion into biomass. The findings of feed conversion ratio (FCR), protein efficiency ratio (PER) and lipid efficiency ratio (LER) obtained in the present study shown in table 2. The FCR in Labeo rohita varied from 2.80 to 6.23 in control and from 2.20 to 4.39 in treatment while in Carassius auratus it ranged from 1.97 to 4.45 in control and 1.57 to 3.18 in treatment. Priadi et al. (2019) [19] reported a similar observation, having FCR values ranging from 2.5 to 3.7 in combined aquaculturehydroponic production systems. The treatment groups had lower and more efficient FCR ranges, which improved environmental conditions and increased feed intake, digestive efficacy, and overall feed utilization. The PER and LER measurements indicated an upward trend. In Rohu, the PER was 0.78±0.01 and 0.94±0.01 in control and treatment, whereas the LER was 5.48±0.09 and 6.60±0.13 in control and treatment, respectively. Similarly, the PER in gold fish was 0.98±0.02 and 1.07±0.01 respectively in control and treatment, while the LER in gold fish was 6.85±0.14 and 7.50±0.11 respectively.

Survival Rate

The survival rate of Labeo rohita and Carassius auratus in the different treatments is shown in the table 2. Survival was discovered at the end of the experiment. In Rohu, survival rates in the control and treatment groups were 95.23±0.06 and 97.50±0.96 respectively. Similarly, the goldfish in both the control and treatment groups survived the experiment completely. Hussain et al. (2022) [24] and Shete et al. (2013; 2016) [24,25] found high survival rates in aquaponic systems. In the RAS system, rohu larvae survived at rates ranging from 80 to 93%. Shete et al. (2013) [24] found that all treatments and controls resulted in a 100% survival rate in gold fish.

Conclusion

The present 60 days study conducted in a recirculating aquaponics system clearly shows that aquaponics can efficiently improve fish growth performance while improving overall water quality. The combination of decorative ornamental fish Carassius auratus (Gold fish) and feeding fish Labeo rohita (Rohu) produced better growth outcomes in treatment system compared to the control. Additionally, Goldfish integration significantly enhanced water clarity, indicating efficient nutrient recycling within the system, whereas rohu grew consistently and promisingly under aquaponic conditions. During the experiment, the initial mean weights of rohu and goldfish (1.34 g and 1.38 g, respectively) increased significantly to the final weights of 6.12 g and 8.85 g. These findings show recirculatory aquaponics promise as an environmentally friendly and resource-efficient method of diversifying fish production while improving growth performance and water quality control.

Acknowledgement

AcknowledgementsThe authors gratefully acknowledge the College of Fisheries Science, Himmatnagar, for providing the required facilities and infrastructure to conduct the present research. The authors are extremely thankful to their research supervisor, Dr. Vivek Shrivastava, for his valuable guidance, continual encouragement, and constructive ideas throughout the course of the study. Special thanks are extended to the non-teaching staff of the College of Fisheries Science, Himmatnagar, for their assistance during experimental setup, sampling.

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