Abstract: A composition comprising starch and lipid characterized by immobility of the lipid in water. A preferred embodiment is a high fat fish food particularly adapted for use as diet of aquarium fish which is prepared from at least one lipid material and starch, advantageously supplemented by further nutrient materials and/or flavoring constituents. The lipid and the starch are so intimately associated with one another in the composition that the lipid component is immobilized, i.e., is not separated from the composition on placing it in water.