How to keep sea monkeys warm?

I live in Canada and it’s quite chilly here. My sea monkey kit should be arriving in the mail sometime soon and I’m not sure what to do. I’ve read that they won’t hatch or thrive if they’re too cold and I’m not sure how to heat the tank. It’s too small for a submersible heater and I’m worried about the heat mat method. How do you heat your sea monkeys? For the heat mat I haven’t found any that were small and I’m worried about them melting the plastic or causing some sort of fire as they’d have to be on 24/7. Should I use some sort of lamp? I just want my first time with sea monkeys to be successful as possible!