50W Submersible Heater

Ok, while strolling through my local pet store in search of add-ons for this already advanced AG Extra Elite. I came across a Submersible heater that claims to keep the water temperature between 76-80 degrees... Is this worth it? I know plants need that 72 - 80 degree temperature range, but what about those roots? Does warm roots = Happy Roots?

My understanding is that the water needs to be on the cooler end of things, otherwise there is potential for root rot. My biggest issue with the AeroGarden 7 is the unit's pump and electronics heating up the water to temperatures far above a healthy limit. I've been using some unconventional, and surely inefficient, ways to try and keep the water temperature down. But this issue still plagues my system.

The reasoning for this heater idea is because during my germination process, my AG is in a room in which the temperature drops significantly at night. So im worried that during those few hours of darkness, my water temp may drop too low. The heater keeps the water at a consistent 72-80 degree temperature. So while the lights are on, I would imagine that this heater would not be on much, but during those hours of darkness it would kick on to keep the water temperature comfortable. This is my first grow, and I am very eager to see YOUR responses.

Define "drops significantly." I believe the lower bound of the heat pump, 76 degrees, might be slightly on the high end or a bit too close for comfort. However, that might be better than very low temps. I'm interesting to hear what you end up doing.