金鱼变黑的原因可能是疾病或水质问题。如果是水质问题，有必要适

金鱼变黑的原因可能是疾病或水质问题。如果是水质问题，有必要适当更换水。最好每周换一次水，以保持水的清洁和卫生。同时，注意温度升高。低温也会刺激它。如果是由疾病引起的，需要先找到疾病的原因，看看粪便、鳃和体表是否有出血，然后根据病情选择适当的药物治疗。

如果你没有治疗水生生物的经验，也没有这方面的足够知识，就不要盲目治疗金鱼。首先，请专家看一看，然后制定详细的治疗方案，循序渐进地治疗金鱼。这是一种更合适的方法

Why goldfish turn black

Goldfish turn black may be due to illness or water quality problems. If it is a water quality problem, it is necessary to change the water properly. It is better to change the water once a week to keep the water clean and sanitary. At the same time, pay attention to the temperature rise. The low temperature will also stimulate it. If it is caused by disease, it is necessary to find the cause of disease first, see if there is bleeding in feces, gills and body surface, and then select appropriate drug treatment according to the condition

If you don't have experience in treating aquatic organisms and don't have enough knowledge in this area, you should not treat goldfish blindly. First, ask experts to have a look, and then work out a detailed treatment plan to treat goldfish step by step. This is a more appropriate method