The effect of stocking density and the application of Nitrobacter as ammonia decomposer in aquaponics system of Clarias gariepinus with water spinach (Ipomoea aquatica)

The effect of stocking density and the application ofNitrobacter as ammonia decomposer in aquaponics system of Clarias gariepinus with water spinach (Ipomoea aquatica)

A.S. Taragusti, P. Fpkunair and B.S. Rahardja

Faculty of Fisheries and Marine, University of Airlangga, East Java, Indonesia

 ² prayogofpkunair@gmail.com,

Abstract

This study aimed to determine the effect of Nitrobacter bacteria on specific growth rate (SGR), survival rate (SR), and feed convertion ratio (FCR) of African catfish (Clarias gariepinus) in aquaponics systems. The sample used was African catfish with a size of 5-7 cm as many as 720 individuals. The research method used was experimental design in the form of Completely Randomized Design (CRD). This study used 5 types of treatments with 4 repetitions. The P0 and P1 contain of 30 fish in each aquarium; 35 fish in P2; 40 fish in P3; and 45 fish in P4. The control group (P0) were treated without Nitrobacter administration and the other 4 intervention groups were given Nitrobacter 1 ml with a density of 1x10⁸ CFU ml^-1. The main parameters studied were SGR, SR and FCR of African catfish in different aquarium with different stocking densities. This research also studied the growth of water spinach (Ipomoea aquatica) also water quality conditions in aquaponics systems. The administration of Nitrobacter in aquaponics systems gave a significant effect on the SGR, SR, and FCR of catfish. The administration of Nitrobacter in an aquaponics system can give maximum effect if there are 45 fish stocking densities and 1 ml Nitrobacter with a concentration of 1x10⁸ CFU ml^-1.

Keywords: African catfish, Water quality, Specific growth rate, Survival rate, FCR

DOI: 10.33899/ijvs.2019.126116.1243, ©2020, College of Veterinary Medicine, University of Mosul.

This is an open access article under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/).

تأثیر کثافة التخزین واستخدام جراثیم النتریة کمحلل للأمونیا فی نظام الزراعة المائیة لأسماک السلور الأفریقی مع السبانخ المائی

ادیندا سبتایساری تراکوستی، برایکو فبکونیر و بویدی ستیا رارهردجا

کلیة الثروة السمکیة والبحریة، جامعة إیرلانجا، جاوة الشرقیة، إندونیسیا

الخلاصة

هدفت الدراسة إلى تحدید تأثیر جراثیم النتریة على معدل النمو الخاص، ومعدل البقاء على قید الحیاة، ونسبة تحویل العلف فی سمک السلور الأفریقی فی أنظمة الزراعة المائیة. کانت العینة المستخدمة هی اسماک السلور الأفریقی بحجم 5-7 سم وباستخدام 720 سمکة. کانت طرائق البحث المستخدمة معتمدة على التصمیم العشوائی الکامل. تکونت تجارب الدراسة من خمسة مجامیع بأربعة تکرارات. احتوت المجموعة الأولى (سیطرة) والمجموعة الثانیة على 30 سمکة فی کل حوض، و 35 سمکة فی المجموعة الثالثة، و 40 سمکة فی المجموعة الرابعة، و 45 سمکة فی المعاملة الخامسة. لم یتم معالجة مجموعة السیطرة بجراثیم النتریة، کما تم إعطاء المجموعات الأربعة البقیة 1 ملیلتر من بجراثیم النتریة بترکیز 1×⁸10 وحدة عد المستعمرات/ مل. کانت المعاییر الرئیسیة التی تمت دراستها هی معدل النمو الخاص، ومعدل البقاء على قید الحیاة، ونسبة تحویل العلف فی سمک السلور الأفریقی فی أحواض مختلفة وبکثافة اسماک مختلفة. کما تم دراسة نمو السبانخ المائی فضلاً عن معاییر جودة المیاه فی أنظمة الزراعة المائیة. أدى إضافة جراثیم النتریة فی أنظمة الزراعة المائیة الى تأثیر کبیر فی معدل النمو الخاص ومعدل البقاء على قید الحیاة ونسبة تحویل العلف فی أسماک السلور الأفریقی. إن إضافة جراثیم النتریة فی أنظمة الزراعة المائیة یمکن أن یعطی اقصى تأثیر إذ کانت الأحواض تحتوی على کثافة تخزین 45 سمکة وبترکیز 1×⁸10 وحدة عد المستعمرات لکل واحد ملیلیتر من جراثیم النتریة.

Introduction

The world of aquaculture is experiencing a rapid development. One of the supporting programs is the aquaculture promotion in various sectors by the Indonesian government. One sector that is being promoted is the freshwater aquaculture. Increased productivity of freshwater fisheries is a government program in welcoming the Minapolitan program (1). Catfish is a commodity of freshwater fish with a fairly high nutrient content. Production of African catfish (Clarias gariepinus) in Indonesia has increased rapidly. In 2004 African catfish production was 55,691 tons, and in 2014 African catfish production reached 543,774 tons with an annual increase of 29.62% (2).

Increasing catfish production required more cultivated land and water use (3). The technology that has been widely applied by farmers in many countries to overcome the problem of limited land is conducting cultivation with an aquaponics system (4). Aside from reducing the land and water use, aquaponics also increases business efficiency through the utilization of nutrients from feed waste and fish metabolism (4,5). Aquaponics constitutes a recirculation system that reuses water which has been used in fish farming with many kinds of filters, such as biological and unbiological filters. One of the plants that can be used is water spinach (Ipomoea aquatica). Water spinach has roots which are not strong and easy to maintain. It requires optimum pH of nutrient solution which is influenced by HNO₃, H₃PO_4, and H₂SO₄ for its growth process (6). These nutrients are obtained by absorbing the existing nutrients through its root. In aquaponics systems, plants absorb nitrates in the waters. The use of water spinach in aquaponics systems is able to reduce nitrogenous fish waste (7).

Fish cultivation with high stocking densities may impair the water quality due to the accumulation of organic matter (8). Factors that cause poor water quality are the remnants of fish feces and feed scraps that are not consumed by fish and are left to pile up and turn into ammonia (NH₃). Ammonia is toxic and dangerous for the survival of fish. The toxic concentration of ammonia in a short period of time ranges from 0.6 to 2.0 mg L^-1 (9). This condition may cause several health problems, such as gill damage, that will further affect feed utilization and growth rate (10-12). One of the effective effort to maintain water quality in aquaponics systems is by adding Nitrobacter bacteria, as these bacteria are suitable materials to improve ammonia decomposition in fish aquarium (12). Therefore, this study was conducted to determine the effect of the administration of Nitrobacter bacteria as ammonia decomposer and stocking density on catfish's’ growth rate, survival rate, and feed conversion ratio in aquaponics systems.

Material and method

Description of the study sites

This research was an experimental study using Complete Randomized Design (CRD). This research was conducted at the Faculty of Fisheries and Marine, University of Airlangga, Surabaya, Indonesia on January 28^th until February 28^th 2018. The independent variable in this study was the density of fish. This study gave different stocking density in each group. The high number of fish would influence the water quality because of fishs’ metabolic waste. The dependent variables were SGR, SR, and FCR of African catfish. SGR is a growth of fish in a certain time, which is shown by fish weight and lenght. It was influenced by water quality, the amount of fish wastes, and feed. SR is the one of parameters that shows the success of fish cultivation which is influenced by water quality. FCR is a feed effectivity indicator and becomes a parameter that uses for increasing fish food intake. There was a Nitrobacter addition as a control variable. Every group was given Nitrobacter as a decomposer for ammonia from fish metabolic wastes. These group would be given the same concentration of Nitrobacter.

Sample

The materials used were African catfish with a size of 5-7 cm as many as 720 fish and Nitrobacter (MSC HIMBIO UNAIR, Indonesia). There were 20 aquaria with (35*25*25) cm long, wide, and height which was filled by local company water about 20 cm height (17.5 L). Fish were fed with commercial feed in the form of HI-PRO VITE 781-1 pellets (PT Central Proteina Prima Tbk, Indonesia) at 6 a.m and 6 p.m. These pellets consist of 31%-33% protein. The average of commercial feed for catfish contain of 28%-32% protein level (13). This meant that feed in this study was very optimal for catfish growth. The water spinach plants were 8-10 cm long. they derived from water spinach seeds that were sown on burnt husk for 2 weeks. They were harvested about 8-10 cm. Furthermore, water spinach was put into a net pot, was made from a plastic cup that has been modified as a way for water entry. Each net pot contained 5-8 water spinach seeds. Burnt husk addition is one way to reduce the use of soil as planting media. After the water spinach were ready, they moved to the trays. There were about 8 water spinach which put in the tray above each aquarium.

Materials

This study used pump set with AT-105 types (Atman) for recirculation. This study also used thermometer Vivid Oval Broader type (Safety), pH meter pen type PH-009 (ATC), DO meter HI9146 (Hanna), digital scale FEJ-5K (Quttro), fish nets 20 cm (PAM), hose 1-meter type (Puso), and ruler 30 cm (Butterfly).

Procedures

This study used five types of treatment with four repetitions in each treatment. The control group got treatment without Nitrobacter addition in the aquarium. Nitrobacter was planted in a test tube the put in an incubator with a temperature of 30^oC about 2-3 days for developing bacteria. Bacterial incubation caused the test tube become turbid. Furthermore, bacteria washed using a centrifuge three times for 15-20 minutes. After the centrifuge appears precipitate, NaCl 0.9% was added so that the bacteria separated from the media. Mc Farland control contained suspended bacteria using NaCl 0.9% solution until turbidity was obtained according to 1 Mc Farland’s standard or aquivalent to 1x10⁸ CFU ml^-1. Bakteria were then countd using dilution formula V₁xN₁ = V₂xN₂. The calculation results showed that the ratio of 1 ml bacterial suspension in liquid form in a microtube is 4:1, so it took 0.25 ml of bacterial suspension and 0.75 ml of NaCl 0.9%. Nitrobacter was taken using a micropupette and blur tip and then pured into each aquarium except P0 group. The 4 intervention groups were added 1 ml Nitrobacter with a density of 1x10⁸ CFU ml^-1. P0 = 30 fish in 15 L freshwater (fish density 2000 m^-3) without Nitrobacter. P1 = 30 fish in 15 L freshwater (fish density 2000 m^-3) with 1 mlNitrobacter. P2 = 35 fish in 15 L freshwater (fish density 2300 m^-3) with 1 ml Nitrobacter. P3 = 40 fish in 15 L freshwater (fish density 2600 m^-3) with 1 ml Nitrobacter. P4 = 45 fish in 15 L freshwater (fish density 3000 m^-3) with 1 ml Nitrobacter.

The optimal stocking density of catfish was about 400 fish m^-3 to 2400 fish m^-3, so that they can grow well. The pattern of treatment aquarium was randomized to avoid bias.

It considered the bias of the treatment happened naturally; and also avoided impartialy to the one treatment. The main parameters studied were catfish specific growth rate (SGR), survival rate (SR) and feed conversion ratio (FCR). Whereas, the supporting parameters observed were water spinach plant growth and water quality conditions such as   temperature, pH, DO (dissolved oxygen), nitrite and nitrate in aquaponics systems.SGR is calculated based on individual weight gain per day with formula (14):

where: SGR = specific growth rate (%/day);

 We = mean of fish weight at the end of fish rearing (g);

 Ws = mean of fish weight at the beginning of fish rearing (g);

 d = total rearing days (day).

SR is calculated based on the number of catfish that can survive during observation in units of percent with formula (15):

Where: SR = survival rate (%);

 Nt = amount of fish in the end of fish rearing;

 Nt = amount of fish in the beginning of fish rearing.

Whereas, FCR is calculated based on the Buwono’s Equation (16):

Where: FCR = Feed Convertion Ratio;

 Wt = weight of fish in the end of fish rearing (g);

 Wd = weight of dead fish during rearing (g);

 W0 = weight of fish in the first day of fish rearing (g);

 F = amount of feed (g)

Measurement of supporting parameters, such as water spinach plant growth and water quality, were carried out manually. Measuring water spinach plants was done by using a ruler, from the base of the leaf to the tip of the leaf. On the other hand, pH and DO were observed every day in the morning at 7 a.m. The water temperature was recorded twice a day at 6 a.m and 4 p.m. However, ammonia, nitrite, and nitrate were analyzed once a week.

Statistical analysis

All data were analyzed using ANOVA (Analysis of Variance) test with SPSS Statistics 21 version. If there was a difference, it was followed by Duncan’s multiple test with significant level  5% (17).

Results

The results of calculating the SGR, SR and FCR of African catfish feed for 1 month can be seen in Table 1.

Based on table 1, it can be seen that all treatments using Nitrobacter on P1, P2, P3, and P4 have higher SGR and SR value than control group. Whereas, the highest value of FCR was in the P0 treatment.

In figure 1, it can be seen that the highest SGR is found in treatment P4 which is equal to 5.0500% and the lowest is found in treatment P0 which is 2.8175%.

Figure 1: Graph of the average specific growth rate (SGR) and feed conversion ratio (FCR) of African catfish.

Whereas, the highest FCR was found in P0 treatment which was equal to 1.07 and the lowest was found in
treatment P4 which was equal to 0.93. In Figure 2 it can be seen that the highest SR was found in treatment P4 which was equal to 92.775% and the lowest was found in treatment P0 which was equal to 41.665%.

Figure 2: Graph of the average survival rate (SR) of African catfish.

Water quality data which includes temperature, pH, DO, ammonia, nitrite and nitrate in maintenance of african catfish can be seen in table 2.

Data on water spinach growth rates, including water spinach length and number of leaves, in the maintenance of African catfish for 1 month can be seen in Table 3.

Table 1: The average SGR, SR, FCR of African catfish

Different superscripts show significant or non-significant differences p < 0.05

Table 2: The water quality average of African catfish maintenance

Initial calculation - week 0, and final calculation - week 4; T = treatment; I = initial; F = final