Originally Posted by Laith
just plug the cable heating into the electric socket and leave it on all the time (it's low voltage so doesn't heat up that much).
Voltage isn't a good way to describe how the cable will heat up the tank. Wattage determines that... I heard the Dennerle cables are low wattage, while Dupla is more into higher wattage, but of course both could be selling both flavors.
So anyway... I think it depends on the temperature of the surroundings. If the place where the tank is remains at a very stable temp, this should work out just great. If the room gets warm in Summer, cool at nights etc you would need a controller.
In my case, I don't use the cables for about 8 months a year, because the tank gets too warm. For the other 3 or 4 months, I plugged the cable into a dimmer (reducing the current --> output) and into a timer, which turns the heater on at nighttime, when the temp of the tank lowered.
Finally I bought a controller (Ranco ETC), but now in Summer I am using it to control the fan that cools the lights.