A set of feeding trials was carried out to assess the potential use of gut weed (GW) Ulvaintestinalis as a direct food to replace commercial feed (CF) in an alternative approach for feeding Spotted scat (Scatophagus argus), Red tilapia (Oreochromis niloticus), and Giant gourami (Osphronemus goramy) juveniles for 60, 45, and 56 days, respectively. Four feeding regimes were assigned to triplicate tanks. The different groups were fed CF every day, GW every day, and one day of CF followed by one (1CF_1GW) or two (1CF_2GW) days of GW, respectively. The results indicated that growth performance of the S. argus fed on single GW was not significantly different from the control group but the performance of O. niloticus and O. goramy in the alternative feeding treatments were comparable to the control. The feed conversion ratio could be reduced by 26.1–57.8 % in the combined feeding regimes to control will minimize the production cost of fish. Water quality in terms of NO2 and NH4/NH3 in the rearing tanks was better in the combined feeding than in the single CF. These results indicated that GW can be used as a food to partially substitute CF for herbivorous fish.