The data were collected from an experiment carried out on juveniles of Gilthead Seabream (Sparus aurata), reared in a Recirculating Aquaculture System composed of three fish tanks. Gilthead seabream were fed three treatments, one per tank: a control commercial feed (with fishmeal and fish oil) (C), a plant-based feed (P), or P + fresh mussel flesh (M). The dataset presented is composed of: 1. Individual fish growth parameters (live weight, length at fork, Fulton’s condition factor (K)), at stocking (S, May 9th 2019) and harvest (June 24th 2019) for each treatment (C, P and M). 2. Overall fish performances measured in group (batch weight, mean weight). 3. Daily quantities of feed delivered for each treatment.