My new betta is obsessed with the heater. He spends most of the day swimming around it. He goes up one side, back down, across the bottom, up the other side, swims behind the cord, and then starts all over. He has been doing this ever since I put the heater in. He NEVER quits no matter if the heater is on or off... I put the heater in 3 days ago. In fact, several times he even freed it loose from it's suction cup, and the heater was floating in the middle of the bowl!
Is he just having fun, or is the heater upsetting him? The heater seems to be working well! It keeps the temp at about 78 degrees.