Tank outside was started on north west corner of my fron porch. Is is outside all the time. On its first night, the low air temperature was 37 degrees. Initially, 20G long tank was to grow seaweed and pods. Because I have tooo many tanks with many hardy corals, I upped the low setpoint from 55 to 65 degrees to include some softies.
Now, because I added a tang, setpoint is 70 degrees.
PS: KW Meter is on 300W heater only. I did not have a heater for the first two nights because bleach was running thru complete system including canister filter & hoses.
3.58 kw at $0.10/kWh equals $.36 cost of electrical heat input for 4 days in February. The big heat input is solar. Temperature swings of 12 degrees are normal for this 20G long tank.