Aqueon Preset Heaters are pre-calibrated to an accurate 78 degrees fahrenheit and require no manual adjustment. Appropriate for most tropical fish, these fully submersible heaters feature a shatter-resistant quartz glass body for added durability. A red LED light indicates that the heater is active, and an automatic shut-off feature works to prevent overheating. Aqueon Preset Heaters are available in 50-Watt, 100-Watt, 150-Watt and 200-Watt models, and come backed by a 1 Year Manufacturer's Warranty.