It depends on the temp the heater is set for, which determines if it's warm enough. It may be warm enough for fish at 23 degrees instead of 28. So if it's 23 in your area, the heater won't turn on. If the temp is 28 in your area, the heater won't turn on - but is 28 too hot for the fish?
Likewise, it's never overly hot in Wgtn in Summer - high of 24 degrees, so if my tanks are set for hotter than that, the heaters are running all the time regardless - but is that temp too hot for my fish?
That's the question