A device and system for monitoring a fluid level within a tank and for indicating when the fluid level within the tank has dropped below a predetermined minimum level. The device includes a strobe light, which is switched on when a sensor determines that the fluid level within the tank has dropped below a predetermined level. The flashing strobe light can be viewed during the day and at night from any viewing angle, and can thereby alert an observer that the tank needs to be filled before the tank becomes empty.