leaning beta after water change

Question
My wife just got a new beta fish and after the first week, changed the water because it was getting dingy. She followed instructions about letting tap water sit for 24 hours in order to dechlorinate. We gently poured the beta into a little bowl, dumped out the water, and cleaned out the tank (did not use soap). Today the little guy is just sitting at the bottom of the bowl, leaning or listing slightly, and is not moving much at all. He is not eating anything either. What did we do wrong? What do we need to do?

Answer
Hello Mark-

Try getting him a heater to warm up his tank. Bettas are tropical fish and need to be kept between 75-80 F or they get very lethargic and can sometimes die if the temperature is too cold. Remember, even if your air seems warm, water without a heater can be 8 degrees lower than your air temperature, sometimes even more if you have fans running.

Hope this helps,
Amber Worman