Temperature problems

[bombilate]

Evening everyone
I am currently cycling my tank but my temp keeps rising IV set my heater to 25 and all was well for a few days then it goes up to 26.5 if I move the heater to a different chamber and turn it down it's ok for a few days then back up...I set it to 24 3 days ago now it's gone up to 25.9 so I figured the heater isn't switching off at the temp IV set it too so I bought a temperature controller today and set it to 25.5 buts been about 5 hours and it's still 25.9 not gone down at all. I don't understand what is happening the heater is brand new and correct size for my tank. The room temperature isn't hot haven't had the heating on etc I haven't even had the LEDs on as it's still cycling. I thought the controller would of worked a little bit by now.

 

[Formulator]

Have you considered your thermometer may be wrong? If two independent electronic thermostats are telling you the water is not as hot as your thermometer says it is…

 

[bombilate]

Ummm no I never said I had different readings bud, I have used 4 different thermometers all say the same give or take 0.2 degrees so deffo not a faulty thermometer

 

[livinlifeinBKK]

Ummm no I never said I had different readings bud, I have used 4 different thermometers all say the same give or take 0.2 degrees so deffo not a faulty thermometer

What lights do you use? If they're LEDs they shouldnt add much heat but other lights can get pretty hot.

 

[gbroadbridge]

What else is running in the tank?

Even the return pump contributes heat, as do pumps in skimmers, etc.

Is the tank enclosed (with a lid) or open topped?
What is the room temperature during the day?

 

[bombilate]

LEDs are not on as cycling still, only equipment is one return pump in the rear chamber and the heater I do have a polycarbonate lid I had made which I have a feeling may be the issue now nothing else makes sense other than it pointing to the lid which I will remove today and see if the temp drops

 

[bombilate]

Update it's actually gone down overnight to 25.4 so the heater is now activated and on. No idea why it dropped overnight and not during the day when I first plugged in the temp controller so hopefully wasn't the lid as it usually goes up at night not down so il keep a eye on it if earns up again il remove the lid and see what happens