We run 4 ten gallon tubs in flower and each has a 50 watt fish tank heater. they can be adjusted to 68f. We have an A/C in the wall running constantly.
The room is always 72f. We are having a cold winter and bad temp swings.
20's at night and 50 to 65 days. Soon it will be 40's at night and 75 to 85 days.

We got the heaters way back cause we were surpised by a night the rez got below 50f. The next day plants just drooped and fell over.