Biocide

1. A dispenser for killing microorganisms in a body of water comprising;

a first housing having a water accessible compartment containing a silver ion donor for releasing silver ions into the body of water when contacted by the body of water; and

a second housing having a water accessible compartment containing a bromine donor and a chelating agent selected from the group consisting of 1-bromo-3-chloro-5,5 dimethylhydantoin, 1,3 dichloro-5,5 dimethylhydantoin, 1,3 dibromo-5,5 dimethylhydantoin, anthranilate, saccharinate and sulfadiazine for releasing the bromine into the body of water, said chelating agent maintaining a biocidal effective level of silver ions and bromine in the body of water when the silver ions and bromine are placed together in the same body of water wherein the level of bromine can be maintained at lower levels than if bromine were used alone in killing microorganisms in the body of water.

2. The dispenser of claim 1 wherein the bromine donor is attached to the chelating agent.

3. The dispenser of claim 1 wherein the second housing and the first housing are located in a dispenser having a set of openings for the ingress and egress of water into the compartments in the dispenser.

4. The dispenser of claim 1 wherein the bromine donor comprises a bromine tablet.

5. The dispenser of claim 1 wherein the bromine donor comprises bromine attached to a hydantoin group.

6. The dispenser of claim 5 wherein the bromine donor comprises a chelating agent.

7. The dispenser of claim 5 wherein the silver ion donor comprises silver chloride.