I have a 10 gallon tank with a filter, heater, and fish tank light. During the cold months last year (which is when I got my first three bettas) the temperature constantly fluctuates. I understand this stresses them out.
Basically when the temperature drops in the tank, the lowest it has dropped if I remember correctly was 76 F, so of course I turn the heater on. I go do something for five minutes and come back the temperature is 86 F. It doesn't stop there though, it'll just keep on getting warmer.
I want to keep my fish warm but not boil them!
I go to school, my parents work during the week. No one will be home during the week days to constantly plug and unplug the heater.
Any tips to keep the temperature from fluctuating?