Aqueon QuietFlow 10 LED PRO Aquarium Fish Tank Power Filter (Up to 20 gal)LED indicator light flashes when water cannot pass through the cartridge, generally indicating it's time to change the cartridge Self priming filter pump will auto start initially or restart if power is interrupted and restored Provides mechanical, chemical, biological and optional, additional specialty pad filtration High flow rates for optimal dissolved oxygen content to promote healthier, more active fish Internal pump design helps dampen noise and