5.5g Nano and heater issues

[Midknight]

Originally Posted by andsoitgoes

Gary - the strange thing is that's not the case at all - I had it down to 75 last night, by the time I checked my tank this morning, it was at 83.7 - Not makin' me happy! I have it positioned right under the outflow of my HOB filter, too.

Ok, this could be your problem right here. If the heater is right under the outflow it will be cooled off but the water flow. This will force it to work harder and heat the tank more.
Try moving it near the intake of the filter that way the warm water is drawn into the filter. This should bring the temp down.
Or if you have the room try the heater inside the filter. That is where I have all of mine.

Dan