The Aqueon QuietFlow LED Pro 50 Power Filter features four stages of filtration–mechanical, chemical, biological and wet/dry–for the cleanest, clearest, healthiest water. Higher flow rates ensure higher dissolved oxygen content for healthier, more active fish. The internal pump design helps dampen noise, eliminates leaks and starts up automatically after cleaning or power interruptions. This new version includes an LED light that flashes when the cartridge becomes clogged, indicating it is time for replacement. The batteries are included for this feature.