i wouldnt just start to raise temp overnight,, during the winter i set my ac3 to 81 degrees,,, so my tank has been acclimated to higher temps throughout the year, I gradually raise the temp by 0.2 degrees per week as soon as spring comes round and drop it the same way when autum rolls round.. this minimises the stress to the livestock rather then a sudden drop.. gotta love a aquacontroller..