A person put warm water in an aquarium thinking that the fish would be more comfortable in it However the fish died What can be the reason for this?

The fish may have died due to rapid temperature changes, as warm water can stress fish that are acclimated to cooler temperatures. Additionally, warm water holds less oxygen, which could have led to oxygen depletion, further compromising the fish's health. It's also possible that the water wasn't properly treated or filtered, introducing harmful substances that contributed to the fish's demise.