Liquid waste of Nata de Coco industry is acidic and contains high organic matter, hence, it requires proper treatment before being released into the environment. This research aims to determine the quality of Nata de Coco industrial wastewater and the toxicity of liquid waste (LC50 96 hours) to goldfish bio-indicators before and after being treated with anaerobic bio-filters. The research phase includes: 1) Liquid waste treatment using anaerobic bio-filters with wasp nest media, 2) determination of optimal processing time duration with variations of 48, 72, and 96 hours, 3) toxicity tests before and after processing such as acclimatization, preliminary, and actual tests, and 4) analysis of research data using probit analysis and linear regression. The results showed that biochemical oxygen demand (BOD) and COD (chemical oxygen demand) values are higher than standard values according to the Regulation of the Minister of Environment of Indonesia Number 5 of 2014, while the pH is lower than the standard value. The optimal processing time duration is 48 hours with a decreased percentage of BOD, COD, and pH of 53.24%, 30.37%, and 46.15%, respectively. The actual LC50 value of 96 hours of liquid waste before and after treatment is 28.20% and 47.21%, respectively.