Pollution has become the serious problem in aquatic ecosystems in Indonesia including east part of the coastal area of Surabaya City. One of the methods that can be used to analyze water quality in the coastal area is pollution index method. The method can provide information related to existing water quality in respect of utilization plan. The purpose of this study is to analyze the water quality in the coastal area in East part of Surabaya City based on the physical and chemical parameters, and then, analyze the data using pollution index method. The sampling points of this study are 10 areas in the coastal area in East Part of Surabaya City. The result of this study showed that the water parameters in the sampling points are described as follows:

Water quality and waste management are significant problems for aquaculture in Indonesia, including catfish (Clarias gariepinus) aquaculture. A combination of Aquaponics Systems and Recirculating Aquaculture Systems (A-RAS) has been developed to address this problem. This study analyzed A-RAS application for catfish (Clarias gariepinus) aquaculture by comparing water quality and production indicators between A-RAS and conventional methods. The results show that temperature, pH, dissolved oxygen, total organic matter, ammonia, nitrate and nitrite in A-RAS technology were 28.0-30.0°C, 6.5-7.9, 3.8-7.8 mg/L, 18.54-24.97 mg/L, 0.12- 0.28 mg/L, 0.12-0.13 mg/L, and 0.04-0.13 mg/L, respectively. Survival Rate, Feed Conversion Ratio, and harvest in A-RAS application were 85.5%, 1.1, and 26 kg/m³, respectively. A-RAS technology can maintain water quality to be reused in cultivation and increase yields by about 13%. Besides, water spinach can be an additional income for farmers.

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One of the main focuses in microbial ecology is the analysis of microbial communities in water, especially concerning bacteria. The results of the analysis related to the abundance of bacteria will be essential knowledge for the development of aquaculture, especially those relating to the dynamics of pond water quality. This study aims to analyze the total abundance of bacteria and water quality dynamics in the water of Litopenaeus vannamei aquaculture that applies a recirculation system. The study was conducted for three months on a concrete pond plot with an area of 2500 m2. Samples of bacterial abundance were taken from pond water, while water quality checks were carried out at ponds and pond outlets. Sampling was carried out at weeks 1, 3, 5, and 8 during the cultivation phase. Bacterial abundance was calculated using Environmental DNA (eDNA), which refers to DNA extracted from the environment without isolating the target organism. The water quality parameters observed were pH, conductivity, DO, turbidity, temperature, and salinity. This study suggested that the abundance of bacteria from the first to the 8th week were 15.3x107; 17.1x107; 36.6x107; and 35.4x107, respectively. Moreover, DO ranged from 3.2 ppm to 7.6 ppm; temperature ranged from 30 °C to 33.3°C; turbidity raged from 12 NTU to 57 NTU; salinity ranged from 19 ppt to 24 ppt; conductivity ranged from 2.93 s/m to 3.54 s/m, and pH ranged from 6.6 to 7.0. This study indicates that the recirculation aquaculture system in Lamongan, East Java may obtain the optimum water quality and controlling the abundance of bacteria to support the aquaculture of Litopenaeus vannamei.

Aquaponics-Recirculation Aquaculture System (A-RAS) technology combines recirculation systems in aquaculture with aquaponics technology. A-RAS technology can reduce water use in the aquaculture system and maintain water quality to fulfill aquaculture standards. The application of this system makes pond water that has been used for fish farming can be reused. This research used a descriptive analysis method to analyze A-RAS's application to improve food production through A-RAS in Kaliuntu, Tuban, East Java. This study's results showed that temperature during the study ranged from 27.