Our aquaponic system established in Waedenswil, Zurich, was a new concept using lightexpanded clay aggregate (LECATM) [13] as filter
medium for the trickling filter. LECA is a type
of clay, which is super-fired to create a porous
medium. It is heavy enough to provide secure support for the plants’ root systems and was used in
indoor and outdoor hydroponic systems [13–17].
LECA was filled in standard boxes (0.4 0.6
0.4 m, green PVC), aligned in three rows in an
adjoining greenhouse (Fig. 1). In total, 74 boxes
were used, holding 3.0 m3
of LECA.