Betta +Eye Bulge

Question
I recently moved my Betta (age unknown) from a small 1 gallon tank to a 3 gallon tank.  All seemed fine.  I had a 25W heater in the 1 gallon during the winter, which kept the water between 75 - 80 comfy degrees.  I put the heater in the larger tank also, but apparently along with the higher powered lid light and the afternoon soon beating directly on the tank (I know...my bad), the water temperature when I came home tonight was up around 90!!  The eye problem was not there this morning, so I suspect he was getting heat stroke.  I immediately took him out of the tank and added a small amount of room temperature water to his cup to start to cool him down.  Will the eye bulge decrease or should I do something else to help him?

Answer
Hi Holly;

Don't cool him down so fast! Let the tank slowly drop in temperature with him in it or he could die from shock. Temperature shock is more dangerous than being in the high temperature. 90 degrees really isn't that bad anyway. Bettas need high temperatures normally of up to 85 just to breed. He should be just fine. Keep him out of the window so the sun isn't on him anymore.

When an eye bulges it is known as "Pop-eye". There are many causes; infection, injury, tumor, toxins. Heat isn't one of them as far as I know. Keep his water very clean and the temperature up to 82 or 85 so if there is infection his body can fight it. I don't think it is a tumor or toxins because these causes take a few days or weeks to have an effect. Is it possible he bumped himself when you moved him to the new tank? If his eye was bumped it could cause swelling for sure. Just keep him warm and clean so he can recover from whatever it is.

Hope he feels better soon!

At Your Service;
Chris Robbins