A dual pump water treatment system for automatically replenishing the water level within a tank of a marine reef aquarium by alternating between a calcium solution reservoir and an alkalinity solution reservoir. The calcium reservoir is in connection with a first pump, while the alkalinity reservoir is in connection with a second pump. The system includes a pair of water level sensors in communication with a solid state relay on a printed circuit board of a switch box. When the water level drops the sensor triggers the relay to turn on the calcium reservoir. When the water level is replenished the first pump is turned off. When the water level drops again, the sensor triggers the relay to turn on the alkalinity reservoir. When the water level is replenished the second pump is turned off. The cycle is repeated based on water level in the tank.