I am currently using a 2.5 gal hex, and am setting up a 5. I'm wondering what heaters you've all tried, and which ones you would suggest. I tired a 7.5 watt micro heater, and it really sucked. Its been suggested that I try out the hydor 25 watt. I just want one that will heat up the tank with a thermostat and not over heat the tank. ie the heating element takes so long to cool off that the water just gets too hot. Thanks!