Through increased interest in the use of macroalgae for biofuel production, the concept of a biorefinery approach has been developed to improve its economic viability. This paper looks at the use of seaweed residue after enzymatic saccharification of the seaweeds Saccharina latissima, Alaria esculenta and Ulva lactuca as a novel feed component for the aquaculture industry. Chemical composition analysis was used to evaluate the impact of enzymatic treatment on the nutritional aspect of seaweed residue. During saccharification, the relative ash and carbohydrate content was reduced, but total nitrogen, total carbon and lipid content increased in all three species. In addition, the saccharification of S. latissima and A. esculenta resulted in the elimination of polyphenols, further enhancing the nutritional value of the residue. The residue supported the survival and growth of bivalve spat and commercially valuable sea urchins over the course of 3-week preliminary trials.