What can be done to get rid of green algae in a pool that has balanced pH and alkalinity and has been repeatedly shocked?

I've actually answered my own question. For anyone who is curious, we used pool floc to treat the problem. Our pool is in an area with a lot of trees, and our problem wasn't algae at all (contrary to what numerous pool "professionals" told us). The greenness of our pool was caused by tree debris that was so fine it went right through the filter. We added floc, which causes all the debris to clump together and sink. Then we vacuumed to waste and our pool was perfect. The whole floc/vacuum process took 24 hours.