Does ozone kill fish

Ozone could kill fish at a high enough level.

However, ozone is commonly used in aquaculture, aquariums, and other applications to keep fish healthy, water clean and clear, and reduce maintenance of tanks.

Check out your local zoo, it will certainly have an ozone system used for the aquariums and aquatic life. This is how they keep the water so clear and blue.

Ozone levels must be controlled very closely as too much ozone can harm fish, just like it can harm us if there is too much ozone in the air.