Heater Deviating From Normal

I bought a 25 watt heater for my 4 gallon tank. It is rated for 3-5 gallons. It is supposed to maintain my temperature at 78-82 F. I started using it a week ago and my tank has been constant at 79 the whole time.

Tonight it has been raising my tank to 82 degrees. Previously when it turned on, the red indicator light would only stay on 40 seconds. Now it has been staying on 50-60 seconds. I am a little freaked out that if I leave it on it may shoot the temperature up overnight. I am losing sleep over this. I don't want to unplug it and have the temperature drop, but am also afraid to sleep. I only noticed this a few hours ago. I unplugged it and let the temp drop back to 79, but it has gone back up to 82.

Am I overthinking this? What is normal for a heater?

 

What is the temperature of the room it is in? How hot and cold does the weather/room get? That is a big temperature swing.what fish do you have?

 

Well today was hotter. The room may have gone to low 80s. But at night it has cooled down. At the point I unplugged I opened windows to cool down the room to maybe 75 degrees and when plugged back in, it still raised to about 81/82. If I unplug it for about 5 hours til I wake up, if the room is about 70 degrees, will a 4 gallon tank lose heat that rapidly?

I do have a back up heater. Maybe that's the best option at this point?

The heater is PGFUNNY 25 watt heater. It has 4.5 stars with 37 reviews. Unfortunately one of them mentions the tank went up to 86 in a 5 gallon. This was about the best 25 watt heater I could find. If anyone can mention a specific 10 - 25 watt heater they know to be good I would appreciate it!

 

If you have a backup I would try that. But it should be fine without one , shouldn’t loose the heat very fast at that temp.

 

Can u tell me what heater it is? I have multiple heaters and the red light comes on when it starts heating. If the tank is at the right temperature then the lights goes off. If your tank only needs a bit of heating then that could be the reason why it only stays on for 60 seconds.

 

The heater is PGFUNNY 25 watt heater. It has pretty good ratings compared to other 25 w heaters. I was concerned because it has been maintaining the tank at 78-79 for a week now. Tonight is jumped up to 80-82 and is staying there. It is supposed to keep the tank between 78-82, but I am concerned because of the sudden change. Is this reason to worry?

 

Okay so just an update in case anyone wants, or this is useful to anyone else. The temperature in my room dropped overnight. The heater has maintained 78 again since then.