Why should the water be slightly warmer than room temperature?
Probably your fish was kept in a bowl at room temperature in the pet shop. Your goal is to get the water in his new home as close as possible to the temperature of the water he is in to avoid shock. Since fish are cold blooded, they aren’t able to regulate their body temperature like we are. Their body temperature is determined by the temperature of the water they’re in. A sudden change in temperature can put stress on the fish and even kill him. The reason I say a little warmer than room temperature is because going from cooler to warmer water (by warmer I mean very slightly warmer) is much less stressful on a fish than going from warmer water to cooler water. So since it’s so hard to get it exactly the same temperature, it’s better to err on the warmer side. But with a little practice you can get it pretty close to exactly the same by testing each with your fingertip until you get it right.
