Analysis of two hydroponic production techniques: floating root and substrate (gravel-coal slag, hydrogel) validated by bioassay in an aquaponics prototype

Abstract

Abstract: In urban areas, improving food production techniques is an urgent necessity due to population growth and socio-environmental factors that limit access to these products in terms of cost, quality, and resource use. This study compared two hydroponic production techniques—floating root and substrate-based (gravel, coal slag, and hydrogel)—tested in a functional urban aquaponic prototype using common carp (*Cyprinus carpio*) and Batavia lettuce. A mixed-methods approach (combining experimentation with analysis and interpretation) was employed. The results highlight that using hydrogel in greenhouse systems provides a suitable medium for more abundant and elongated root development; furthermore, it allows for a shorter harvest time due to the material's capacity to retain nutrients and water. Successful reproduction of the animal species within the system was also achieved.