r4k

My tank is about 24 gallons and currently using a 150 watt heater (aleas) in it..I've set the heater on 72degrees (the minimum the heater allows). However, the temperature is now at 84degrees.

I turned the heater off this morning because even though I set it to 76degrees last night, the water temperature rose to almost 90degrees I turned it back on in the afternoon because temperature dropped to 72degrees, so I turned it on to 72degrees but now about 8 hrs later, the temp is now at 84-86degress

I thought that it may be because of the internal filter (aqua one maxi 103f) but shouldn't the heater turn off automatically when the temperature rise above the temperature set on the heater?

mitch

sounds like you have a bad heater. Get one that has a light when is comes on. Remember if the temp in the room is higher than what the heater is set at, it will rise

Fishies-for-me

The heater should cycle on and off according to the temp of the room...if it is hotter in the room than you have the heater set for it should not come on at all. If it is colder in the room the heater should cycle on and off every few minutes to maintain the proper temp....sounds to me like you have a faulty heater and all the heating and cooling the tank is going thru is not good for the fish...you should replace it...good luck.