I'm currently in the process of upgrading from a 2.5 gal tank to 5 gal. I decided to spend a little more money and upgrade to a better heater as well and I purchased the Aqueon Submersible 50 watt heater recommended for 5-20 gal tanks. I set up the new 5 gal tank last night and set the heater up according the directions. The original setting on the heater is at 80 degrees and the instructions recommended that the heater run on this setting for at least 24 hours before adjusting the temp. When I got up this morning and checked the new setup (no fish in yet, he's still in his old tank) the temp of the water was 76 degrees, which seems a little low to me considering the setting of the heater is at 80. Also, the light on the heater indicating that it's running keeps going off and on. The directions state that the heater has an automatic shut off to protect against overheating, but they don't state whether this on/off function is normal. Does anyone have any experience with this particular heater and, if so, can you tell me if this functioning sounds normal? I would like to get the water a little warmer (I would feel better if it were between 78-80 degrees) but if the heater is not working properly then I suppose I'll have to exchange it for a different one. Any comments or suggestions? Thanks!