I use an eheim jager heater in my 10g. I've had it for about three years and it's still working fine.
Those are Cobalt heaters. I've not used them personally, but I've heard good things about them.I have a Neo-Therm heater. It is awesome.. Works very well. You pay a bit more -- but for $10 or $15 bucks.. I think it is well worth it. You can find the right size for you easily on Amazon.