Originally I was running a kit heater (50w preset 78) in my 10g. Yesterday I upgraded to an adjustable 100w heater from aqueon (only thing I could find local). I set the temp to 80. The first few hours my thermometer read 79 and the heater was heating. Then the temp dropped to 78.8 and then would heat back up at 78.6. This morning I woke up and the temp was 78.4 and heats back up to 78.6. My filter is located on the short wall about 8 inches from the heater. My thermometer probe is between the two. I’m a little worried my new heater is not going to heat my tank properly and I’m not sure if this is normal or not. I still have my old heater and have considered adding it in as a second heater. Not sure what the best plan of action is here. Thanks for reading!