I have a 10 gallon betta tank that currently has an Aqueon Pro adjustable heater. I purchased this heater in late January when I started the tank. The heater had kept the temperature at a steady 79°F, but all of the sudden I checked my tank thermometer last week and the temperature was 84°F even though I have it set at 79°F. I turned the dial on the heater down to 76°F to try to drop the temperature, and it dropped to 82°F which is still a little too high for my liking. I thought maybe my thermometer was broken, so I got a new one and it shows the same temperature the other one did. For this reason I want to get a new heater. I've heard great things about Eheim heaters. What brand would you guys suggest for a 10 gallon tank? Thanks!