Zoo Med’s Plankton Banquet® time release feeding blocks last 3 to 14 days, depending on block size. In addition to weekend and vacation feeding, Plankton Banquet® is a great daily food source for problem feeders such as Plecostomus, Algae Eaters, Redtail Sharks, Gouramis, Saltwater Tangs, Angels, Damsels. Original Banquet® blocks are also useful for small fry which do best when constantly feeding. Now with twice the plankton! Contains blue-green Spirulina chunks. Great for bottom feeders. Formulated for fresh and saltwater fish. Do not use this product in fish bowls or aquariums which do not have aeration or filtration. Plankton Banquet® blocks will not cloud water. Important: The blue color in this block is pure spirulina. Spirulina is a blue-green plant plankton rich in raw protein and major vitamins. Research has shown that fresh and saltwater fish exhibit superior growth, maturity, energetic behavior and more elegant coloring when fed spirulina. Available in the following sizes: Original: Duration is 7-8 days. 0.45 oz (12.8 g) Giant: Duration is 10-14 days. 1.4 oz (39.7 g)