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.