Giant grouper juveniles were produced from a single cohort at the Pacific Aquaculture and Coastal Research Center, UHH according to larval rearing and nursery protocols described for the species.
Prior to the start of the trial, all fish were fed with commercial marine fish diets.
All diet treatments were tested in triplicate in a feeding trial that lasted 12 weeks, diet treatments were randomly assigned to the tanks.
Seventy-two fish with an average initial weight of 45.9 g+ 7.1 were distributed in a 4.5 m3 sea water recirculation system with twelve 90-L tanks at a density of six fish per tank.
Fish were manually fed to apparent satiation twice per day at 08:00 and 16:00 h.
Daily feed intake and fish mortality were recorded.
A photoperiod of 12L:12D was maintained throughout the trial.
A partial seawater exchange (30% total system volume) was performed once each week.
Water quality parameters were monitored daily with a portable multi-meter and maintained at the following averages: temperature 24,8 t 0.7 C, dissolved oxygen 6.6 t 0.3 mg L salinity 34.0 t 0.5 ppt.
The water pH (7.7 t 0.2) and total ammonia nitrogen were measured three times per week with a colorimeter.