Can I save my Koi after using copper sulfate in my small pond?

Using copper sulfate in a pond can be harmful to fish, including Koi, as it can lead to toxicity depending on the concentration and duration of exposure. If you've used copper sulfate, it's crucial to monitor the water parameters and consider performing a water change to dilute the copper levels. Additionally, using a water conditioner that binds copper may help reduce its toxicity. However, the chances of saving your Koi depend on the amount of copper used and how quickly you act.