2.5 gallon with heater... issues

[MADxMAC771]

Hey all. I just got a heater for my 2.5 gallon today. Its a small paddle heater with no thermostat. According to the box it is designed to increase the temp of a tank about 5 degrees. Well, my average tank temp for the past week has been 73. It was getting a little low due to the cold weather so i figured i would go get a heater. I put the heater in and plugged it in and all seemed to be fine. The temp started climbing (very slowly). Right now it is right around 80. From what I can tell, however, it doesnt seemed to be stopping. its reaching over the 80 degree mark and Im concerned with how high it will go. I just plugged it into a timer to have it go on and off in 30 minute intervals to hopefully level the temp. What is the max temp that I should allow this to get to? I have my eye on a few heaters online right now that have preset thermostats at 78 degrees. Any one have any heaters they like that work for a 2.5 gal?

[iamntbatman]

Honestly, 2.5g of water is a real pain to heat. The tank is so small that water changes happen really rapidly. I've always had problems with preset heaters overheating tanks in that size range. I'm not sure if using the timer is a good idea or not, as I'm not sure how the heater will handle the stress of being turned on and off like that. However, if it keeps your water at 80*F, I think that's perfectly fine. Even 82 would be an acceptable range for a betta. One you break 85 or so is when you really need to be concerned.

[MADxMAC771]

for a while the timer Idea was working. keeping it at a steady 78 in off and on invervals of 30 minutes. The temperature is getting lower and lower here so more heat was necesarry and I changed it to a 45 on 15 off interval which kept it at about 77. I woke up this morning to find his tank had gone down to 73, so I said screw the timer and just plugged it in. It was only reaching the mid 80 range while it was 70 or so degrees outside. Lately its been in the low 60s so hopefully this will balance out.