What kind of thermometer? Some can be "off", its good to compare a couple different thermometers, or try to calibrate them or get used to how they read.
If you take it out and sit it next to your thermostat in the house it should read the same.
Water temps raise and lower much slower than air, so if you temp is 80's in the day in your house for like the last couple days, then it gets cooler one day, the tank wont drop much compared to the house temp.
10G,Planted- Endler's Livebearers+RCS, 55G,planted
Originally Posted by Kurt_Nelson
Understanding the basics will let you make informed decisions on what advice to follow, and what advice is just plain hooey!