There are several steps that can be taken to maintain water quality in a fishing pond. First, regular testing of the water should be conducted to monitor pH, temperature, and dissolved oxygen levels. Second, the pond should be stocked with appropriate amounts of fish to prevent overpopulation and oxygen depletion. Third, aquatic plants and algae should be managed to prevent excessive growth. Finally, any pollutants or chemicals should be kept out of the pond, and regular maintenance of the pond's filter and pump should be performed.