The land in West Oakland where Eric Maundu is trying to farm is covered with freeways, roads, light rail and parking lots so there's not much arable land and the soil is contaminated. So Maundu doesn't use soil. Instead he's growing plants using fish and circulating water.
It's called aquaponics- a gardening system that combines hydroponics (water-based planting) and aquaculture (fish farming). It's been hailed as the future of farming: it uses less water (up to 90% less than traditional gardening), doesn't attract soil-based bugs and produces two types of produce (both plants and fish).