Aqua One Spirulina Flakes are an excellent addition to your tropical or goldfish's diet. Spirulina is planktonic blue-green algae that is not only rich in protein and a variety of minerals, but is also fantastic for boosting your fish's immune system, it stimulates the production of antibodies which will increase resistance to illness and disease. In addition, Spirulina is highly digestible making it a nutritionally dense food source for your aquarium fish.