Sera Marin Spirulina Grazer XL is designed for mainly herbivorous fish including tangs, angels, and wrasses. These tablets are designed to sink to the bottom or, with slight pressure they can be attached to the aquarium glass! This encourages even shy fish to come out of hiding for a bite to eat. The high amount of spirulina algae in these tablets (21%) helps support healthy digestion, vivid color, and vitality in the fish. This food also encourages natural foraging behavior in the fish.