Its possible. I live in Wisconsin. It gets damn cold here. Everyone knows that.
When I was a broke bachelor I lived in a total dive apartment with vaulted ceilings, bay windows, and literally no insulation. Huge place, about 130 years old. We didn't have any money, it cost us damn near $300 a month in gas just to keep the place between 50* and 60* during the day in the dead of winter. at night it dipped even colder. Maybe High 40's. We Didnt nead a coat rack, you came in and just kept it on lol. Really convenient.
I tossed blankets on my 75g at night which sat in front of the bay window. It stayed at 76* all winter with just 2 150 watt heaters. They were pretty much on all the time though, and 300w is a little low for a tank that size imo.
My basement gets into the low 50's during the winter at my new apt. I've got one tank down there that I insulated with blue foam, it stays at temp without the little red light being on constantly.
I would think with a good controller and enough watts you'll be fine. Insulation makes a huge difference. Just be ready to pay the power company.
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