How do you keep algae out of bird bath without harming the birds?

Use a solution of one part chlorine bleach to nine parts water to scrub the bath thoroughly. Scrub the basin, lip, and any area of the bath where birds land, perch, drink or bathe. Rinse the bath out thoroughly with water until nothing foams and allow it to dry in direct sunlight which will break down any remaining chlorine residue.

Vinegar and coarse salt will work. Depending on the size of the bird bath... Amount to use is: 1 cup vinegar ...pour into bird bath Scrub. with stiff brush then use 1/2 cup coarse salt...continue scrubbing..then...rinse thoroughly. ( Repeat process if needed usually only one good scrubbing is needed) Finally... Fill with clean water for the birds.

Once thoroughly cleaned, changing it's water daily will keep it clean.

Keep out of the sun