Growth Performance of Daphnia sp. Cultured in Different Concentration of Rice Washing Water

This study aimed to investigate the effect of the administration of rice washing water in culture medium on the growth performance of Daphnia sp. This research using three different doses of rice washing water i.e 1 mL/L, 3mL/L, and 5 mL/L. Daphnia sp. was cultured with an initial density of 20 ind/L. Observed parameters include growth parameters (population density, size and specific growth rate) and water quality. This result showed that a concentration of 3 mL/L created the highest population of Daphnia sp. density about 620±20 ind/L, number small size (young stage) 81.2%, and the highest specific growth rate about 56.68±0.55%. The water quality content of DO, temperature and pH during this study were in the good range of Daphnia sp. life and reproduction. The research has a conclusion that rice washing water can be used to nutritional sources of Daphnia sp. In the future, it is necessary to make further observations about the reproductive performance of Daphnia sp, given rice washing water through clone culture.


Introduction
Aquaculture is the production of aquatic organisms and plants on controlled conditions [1]. Presently, Aquaculture is one of the promising agriculture activities that growing rapidly around the world and has the potential to improve food security [2]. The success of aquaculture production depends on the all phase in aquaculture include broodstock holding, hatchery production of fry, nursing system, and grow out to market size [3]. Especially in fish larval farming on the hatchery, the obstacle is the availability and quality of live food at the right amount and size that suitable for the mouth size of the fish larva at the time of the first feeding.
Live food is used as a carrier of nutrition for the larval stage of aquatic animals [4]. Daphnia sp. is one of the potential live feeds that has been cultivated to meet the nutritional needs of freshwater fish hatcheries. The advantages of using Daphnia sp. for live feed in hatcheries due to its low cost and nutritional content [5]. The growth and development of Daphnia sp. are affected by nutrition, therefore alternative nutritional source that can increase the Daphnia sp. population is needed to maintain the availability of Daphnia sp. as live feed for the fish larvae. Rice washing water is one of the potential alternative nutritional sources for Daphnia sp. According to Laila [6], rice washing water is containing optimal nutrition to support the growth of Daphnia include Vitamin B1, Vitamin B3, Vitamin B6, Fe, natrium, phospor, and kalium. This study aimed to investigate the effect of the administration of rice washing water on growth population, size, specific growth rate, and water quality of Daphnia sp.

Research on Weather Predictions
The rice washing water is obtained from the washing of rice with water at a ratio of 1:1 (w/v). After that, rice washing water were was allowed for 5 minutes [7].

Preparation of Daphnia sp.
Daphnia sp. used in this study were isolated from a fish pond in Serang Regency, Banten. The stock was cultured in an aquarium with a capacity of 25 L and feed with yeast Saccharomyces cerevisiae [8]. The individuals used in this study were adult stages that had a lenght of 2 mm±0.4 mm and a width of 1±0.2 mm.

Rearing of Dapnia sp.
This study was conducted at Aquaculture Laboratory, Department of Fisheries, Faculty of Agriculture, University of Sultan Ageng Tirtayasa. A total of 20 ind / L Daphnia sp. were reared using an aquarium with a size of 30 cm × 30 cm × 30 cm (l × w × t). Each aquarium is filled with 3 L of water an added aeration of 0.12 L/min. The study used three treatments of adding rice washing water in the culture media of Daphnia sp. (mL/L), i.e. 1 (treatment A), 3 (treatment B), and 5 (treatment C). Each tratment was repeated three times. Daphnia sp. culture is carried out for eigth days. The water (20-25%) of this culture was replaced every three days. Water quality, namely temperature, dissolved oxygen (DO), and pH, is measured every two days to maintain water quality. Temperature is measured using a thermometer (°C), DO with the use of DO meter, and pH using pH meter.

Observation of Dapnia sp.
Observation for the abundance of Daphnia sp. was conducted every day to counting the population of Daphnia sp. The size of Daphnia sp. was observed on the last day of culture. Length and width measurements are performed using ImageJ software. Size is characterized into three groups namely, small (S), medium (M), and large (L), based on length and width ( Figure 1). Size S has length 0.82-0.92 mm and width 0.46-0.55 mm, size M has length 0.93-2.14 mm and width 0.82-1.25 mm, and size L has length 2.15-3.19 mm and width 1.26-1.56 mm.

Data analysis
The population density and specific growth rate data were analyzed using Analysis of Variance (ANOVA) and for those with differences were subjected to Duncan Multiple Range test with a 95% confidence interval. The percentage of size Daphnia sp. and water quality were analyzed descriptively.

The population density and size of Daphnia sp.
The Effect of three different dosage addition of rice washing water on the population density of Daphnia sp. is presented in Figure 2. The densities of Daphnia sp. were cultivated on medium containing rice washing water with a concentration of 1, 3 and 5 ml/ L increased until the 6th day, then decreased on the 7th and 8th days. The highest peak density of Daphnia sp. given rice washing water was achieved on the 6th day. Similarly, the previous studies showed that that the peak growth density of Daphnia sp. occurred 6 days after the administration of tofu and bran fermentation [9]. Treatment B showed the highest density of Daphnia sp. which was 620±20 ind/L that was significantly different (P<0.05) from treatment A which was 180±50 ind/L and C was 580±15 ind/L. According to Lawrence [10], the growth and development of Daphnia sp. were affected by nutrient, age, temperature, and filtered particle shape. The result showed that Daphnia sp. can utilize nutrients from rice washing water so that it can increase the growth of the Daphnia sp. population.
Besides, the size of Daphnia sp. on the last culture day showed that all treatments produced more small size Daphnia sp (length 0.82-0.92 mm and width 0.46-0.55 mm). The number of small sizes or young Daphnia sp. indicate that rice washing water supports reproduction of Daphnia sp. Treatment B produced the smallest size of 81.2% (Figure 3.). These results need to be observed further to observe the reproductive performance of Daphnia sp. given rice washing water through clone culture.

Specific growth rate
The Effect of the addition of three different dosages of rice washing water on specific growth rate of Daphnia sp. is presented in Figure 4. The result showed that the Daphnia sp. highest significant (P<0.05) survival growth rate was found in treatment B which was 56.68±0.55% followed by treatment C was 55.63±0.45%, while the lowest survival growth rate was found in treatment A was 40.67±3.74%. According to [11] Daphnia sp. requires adequate nutrition from food to reproduce and grow therefore resulting in a multiplied population increase that affect specific growth rate value. While in treatment A, the nutrition from rice washing water to Daphnia is insufficient, therefore showed a low specific growth rate.

Water quality
Growth of Daphnia sp. influenced by water quality. In this study, water quality was maintained in the ideal range for Daphnia sp. The result of water quality showed in table 1.  The mean DO value in three different treatments in this study was 7.45±0.08 mg/L -7.6±0.00 mg/L. According to [12], DO in culture media supports the respiration of Daphnia sp. without creating competition between Daphnia sp. and decomposing microbes. So, Daphnia sp. can utilize optimum DO for metabolism to growth and reproduction. Daphnia sp. can survive in DO >3 mg/L, but they grow better at a minimum of 6 mg/L.
The mean temperature value in this study was 27.57±0.07 °C -27.63±0.06 °C. According to [13], the ideal temperature for the growth of daphnia was 25-30°C. In cladocerans, food activity depends on the temperature of the concentration of food. Therefore, better performance of reproductive and growth is expected from populations where there are nutritional conditions of abundance and appropriate temperatures [13].
The mean pH value in this study was 7.58±0.04 to 7.61±0.11. The ideal pH for the growth of Daphnia sp was 7-8.6 [1]. According to Darmawan [14], the pH affects the egg's life span of zooplankton microcrustaceans include Daphnia, and pH determines the toxicity of medium from ammonia. The ideal pH of Daphnia sp. was 7-8.6.

Conclusion
Rice washing water can be used as an alternative nutritional source for Daphnia sp. The addition of 3 mL/L rice washing water was the best concentration to the growing population, number of small size (young stage), and specific growth rate of Daphnia sp.