I'm currently using flexwat brand heat tape. I know that is what a lot of people are currently using, but now there is a new brand of heat tape that is sold by reptile basics that is supposedly superior and safer than flexwat. I think the brand is THA, don't quote me on that.
The only thing with heat tape is that you must use a thermostat with it. Also if the connections are made properly and the heat tape is mounted correctly, problems shouldn't occur too often.