H2Pro Stealth Heater 100W is a good product that design to maintain a good range of temperature in the aquarium. It has a power cord with the black color design. It's easy to set up and it'll fit any size of the aquariums. This product is fully submersible that can be placed in the aquarium vertically or horizontally. If the temperature has not changed since installing the product after 24 hours or more: check if the temperature has been set and the product has been plugged in correctly. Make sure that the product is submersed to the minimum water level (vertically and horizontally). Make sure there is water circulation around the product. If the temperature is too high, check the water levels for evaporation. If the water is too low, add water immediately.