When I 1st setup the tank i plugged in the heater & turned it to 22 degrees. 12 hours later I checked the temp. it was nearly 25 & i turned the heater down to 18. Next reading was nearly 24 so i unplugged the heater (will look at calibration in due course). The next reading was just under 23. This seems odd as the room ambient temperature is 21. Just checked the temperature again and its 22.6. Is there something in the chemistry up of a new sett up that generates heat? I appreciate there's a bunch of electrical equipment and lights but all that is cool to touch.