Tetra Holiday fish food for tropical fish is a healthy vacation food that provides optimum nutrition of fish during an absence for up to 14 days. The Tetra Holiday block is 100% edible, and contains essential vitamins, trace elements, minerals and tasty daphnia. It is a long term solid in the water that can be used without polluting the water. Number of blocks depends on number and size of fish, days of absence and aquarium size.