Most use those tiny 2.5W heat mats, better than sticks, flow through units etc.
The idea of cables is a bad idea on a few levels, if it is about getting stuff out of a tank, the the mat is the best solution for a nano.
Cables do not do what are claimed, no one to date, and after what? 25 years now, has shown otherwise. Only vendors claims..nothing for support other than this.
I've challenged many to this, test, experimental designs etc.
Not one has come forth with any evidence or test, heck even a little bit of knowledge on the topic.
But they keep making and marketing them.
They do heat the water, that's about it, like any heater.
The rest? Rubbish.
However, for a nano tank, the heat mats make a lots of sense, not due to cable "quackery", rather......ease of use for such a small tank.