In an aquarium with no flow, fish and corals begin to die in as little as 4 to 10 hours. The VorTech Battery Backup is reef tank insurance in an aluminum housing. By adding the VorTech Battery Backup, your tank is insulated from power interruptions for up to 36 hours with the MP40w and up to 72 hours with the MP10 and MP20. Can connect to another Battery Backup for two times the run time. Comes with trickle charger so you're always prepared, and includes all required wiring cables. 18 Amp-Hour 12-volt sealed battery.