Spirulina powder is a super concentrated source of nutrients, high in protein, rich in gamma linolenic acid, vitamins, minerals and other bioactive substances. The thin cell walls make it easy to digest and it can help improve your dog’s immune function and support growth. Spirulina is a fresh water cyanobacterium (algae) which is grown in greenhouse ponds fed by spring water and this is harvested, dried and milled to a fine powder.