50 watt Heater on a Waterbox 10 gallon

[Big Mistake]

For the record a Cobalt Aquatics 50 Watt Neo-Therm can keep a Waterbox 10 gallon at 78 F.

But ... when the environment is down around 63 F it can't keep it at 80 F.

Heater is on constantly and just can't quite get it to 80 F.

Unless covered. Then it can.

Just saying.

I kinda suspected from other tanks there would be a problem during the winter.

-Big Mistake

PS At 5380 feet above sea level in Colorado. Dry condition lots of evaporation.

 

[Subsea]

Convection heat exchange is one source of heat loss. Evaporative cooling of water with dry air is substantially more of a heat loss. When one pound of water evaporates 1000BTU are transferred during that phase change of water to vapor. One gallon of water weighs 8.34 pounds.

Also, 80 degrees seems unnecessarily high for a reef tank and for many tank inhabitants, it is stressful. I assure you that any bacterial infections will bloom exponentially with that temperature.

PS. I have several hundred gallons of open top tanks with no electric heaters but plenty of heat gain from lights & pumps with systems running between 75-78 degrees.