Check out the low tech and nano forums... A few years back, planted bowls were really popular and I saw a few (at the time) very successful dirted, no-tech bowls. I don't know how they turned out over the years, though. That said, I wouldn't really recommend going the no heater route seeing as you live in Canada... It's not impossible but it will severely limit the kind of livestock you can keep. If you want really any fish besides maybe white cloud minnows, you're going to want a heater. Shrimp can be kept in colder waters but still like temperatures in the low to mid 70s (Fahrenheit).