The Wilma Systems come in 2 sizes 11L and 18L. These systems can be used with any growing medium including soil, coco, clay pebble or rockwool. Within the Wilma Systems, the nutrients are stored in the base of the system. A water pump is then used to circulate the nutrient solution through the drip-lines and out through drippers inserted into each pot. Once this is complete the solution is then returned to the reservoir to be used again.