Abstract: A method for treating a recirculating water system which comprises introducing into said water system a multifunctional, multilayer tablet, wherein the multilayer tablet comprises a fast dissolving layer and a slow dissolving layer, wherein said fast dissolving layer releases a combination of active ingredients including a member selected from the group consisting of lithium hypochlorite, calcium hypochlorite, trichloroisocyanuric acid (TCCA), anhydrous sodium dichloroisocyanurate, sodium persulfate, potassium persulfate, potassium monopersulfate, sodium monopersulfate, and mixtures thereof, and at least one of a clarifier, chelating agent, sequesterant, algaestat, water softener, algaecide, corrosion inhibitor, scale inhibitor, flocculent, disintegrant, dispersant, colorant, dissolution control agent, fragrance, or surfactant and, wherein said slow dissolving layer includes a member selected from the group consisting of trichloroisocyanuric acid (TCCA), calcium hypochlorite, 1,3-dichloro-5,5-dimethylhydantoi

Abstract: A method of providing a solid oxidizer to a tank of water, while also providing a way to indicate when it is time to add more oxidizer. The preferred method includes providing the solid oxidizer in the form of an oxidizer shell with a coloring agent disposed therein. The coloring agent is substantially color stable when stored in the oxidizer shell, and the oxidizer shell is formed and shaped to enclose the coloring agent in a manner in which the coloring agent is prevented from dispersing into the water until the oxidizer shell is substantially dissolved.