JBL Holiday serves for the nutrition of your fishes during the vacation. It contains all constituents, which are necessary for a healthy nutrition: Grain, fish and fish by-products, vegetable materials, yeasts and algae. JBL Holiday supplies 20-25 medium sized fish about 2 weeks long. That food stone is put in the aquarium. There it resolves itself slowly, without clouding the water. Depending on water hardness, the cubes may dissolve quicker or slower.