Abstract: Disclosed are an apparatus and methods for introducing additives into a fluid flow. An additive vessel, with chambers for one or more additives, is attached to a primary flow fixture in a configuration that permits a diversion of part of the primary flow through the additive vessel then back to the outlet of the primary flow fixture. When the apparatus is engaged, a part of the primary flow is diverted to the additive vessel, combines with the additive, and then is re-introduced to the fluid stream, exiting the primary flow fixture.