An apparatus for treating water in soil-less growing systems has a container having a cross-sectional area and a height, with a first access port for liquid at an upper end, and a second access port for liquid at a lower end, and a porous matrix filling the container, the matrix comprising a hydrophilic polymer mixed with rocks and natural minerals. Water drawn from a soil-less growing system, is urged into the container through one of the liquid access ports, causes the water to flow through the matrix in the container, the water in contact with the rocks and natural minerals in the matrix, leaching elements from the matrix, and causes the water to exit the container at the other of the liquid access ports, to flow back to the soil-less growing system.
