Chickens will usually start to build up resistance to the coccidia in the soil around 11 to 20 weeks old, so it wouldn't hurt to give another treatment for 5 days (only the lower preventative dose below) around 3 weeks from the previous treament. Keep in mind that many people treat the disease differently, so reading some threads by doing a search at the top of this page may be enlightening. Here are some good links to read about the disease.
http://www.the-chicken-chick.com/2012/12/coccidiosis-what-backyard-chicken.html
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex4616
http://www.merckvetmanual.com/mvm/poultry/coccidiosis/overview_of_coccidiosis_in_poultry.html
The preventative dose (.006%) for Corid Powder is 1/3 teaspoon.
The preventative dose (.006%) for Corid liquid is 1/2 teaspoon.
The moderate outbreak dose (.012%) for Corid Powder is 3/4 teaspoon.
The moderate outbreak dose (.012%) for Corid liquid is 1 teaspoon.
The severe outbreak dose (.024%) for Corid Powder is 1.5 teaspoons
The severe outbreak dose (.024%) for Corid liquid is 2 teaspoon.
http://www.the-chicken-chick.com/2012/12/coccidiosis-what-backyard-chicken.html
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex4616
http://www.merckvetmanual.com/mvm/poultry/coccidiosis/overview_of_coccidiosis_in_poultry.html
The preventative dose (.006%) for Corid Powder is 1/3 teaspoon.
The preventative dose (.006%) for Corid liquid is 1/2 teaspoon.
The moderate outbreak dose (.012%) for Corid Powder is 3/4 teaspoon.
The moderate outbreak dose (.012%) for Corid liquid is 1 teaspoon.
The severe outbreak dose (.024%) for Corid Powder is 1.5 teaspoons
The severe outbreak dose (.024%) for Corid liquid is 2 teaspoon.
