This study aimed to identify pathological agent and determine the impact of water quality during climate transitions on mass mortalities of neon tetra (Paracheirodon innesi) in the West Java region of Indonesia. Ten thousand fishes reported died each day during the seasonal. Samples of 10 fish/tank were taken and tested for parasites, fungal, and bacteria. The investigations tests showed that the primary disease was caused by parasite from protozoa Pleistophora spp. (Microsporidia). It was confirmed by taxonomic descriptions and histopathological diagnosis. This parasite causes histozoic infection. Fungus was not detected, and bacteria were identified as Aeromonas sp. and Pseudomonas sp.. The water temperature fluctuation was recorded higher than 7°C between daylight and night. Mortality was recorded in every size of fish. The clinical signs of fish on the outbreak were pale body, discoloration of the lateral line, the appearance of white patches under the skin, lethargy, swimming disorder, and losing weight. The recommendations due to the outbreaks were total eradication for infected fish populations, separating newly arrived fish (quarantine) at least 2 weeks, maintaining water quality in the optimal range, and proper cleaning (sanitizing) must be performed.

Prebiotics are undigested food ingredients that can be utilized by intestinal microorganisms. The provision of prebiotics will improve growth performance, inhibit the growth of pathogens, and increase fish immunity. Several previous aquaculture studies have used single prebiotics as prebiotics, such as FOS, GOS, and inulin. We need a material that is multi prebiotics which is expected to give better results. Honey is a material that includes multi prebiotics. The purpose of this study was to evaluate the administration of prebiotic honey with different doses (0%, 05%, and 1% doses) through feeding on the diversity of microbiota in the digestive tract of tilapia (Oreochromis niloticus). The method used in this study was to take samples of tilapia intestines, then analyzed them using Next Generation Sequencing (NGS). The results showed that the most unique OTU were in the treatment of prebiotic honey with a dose of 1%. The treatment of prebiotic honey in the feed gave a higher OTU compared to the control. This is because the oligosaccharide content of honey can be utilized by the gut microbiota. The high unique OTUs in the treatment of adding honey, both 0.5% and 1%, presumably because these unique OTUs can grow well in that environment so that there is an equilibrium between species that together can utilize nutrients from honey oligosaccharides. so that all components of the microbiota can grow optimally. Prebiotic honey given to tilapia also triggers the emergence of the genus Lactobacillus, Cetobacterium, and Clostridium sensu stricto which are probiotic bacteria in the fisheries sector.