from the information given, my expert opinion is that someone is throwing a party in the left side of the tank.
please post a pic of the tank and room outside the tank. did you check the params on both sides of the tank, and is there circulation between the 2 sides? is your heater on one side? does the dog always stare at them on the right side? is the left side facing north, south, east, or west? more info would be great, and it would prevent us from wasting time asking questions