Portland, Ore., moving to add fluoride 12 (UPI) -- An anti-fluoride group said it would seek a referendum after the Portland City Council voted to add the cavity-fighting chemical to the Oregon city's water. The City Council voted 5-0 Wednesday to have fluoride put in Portland's drinking water, The (Portland) Oregonian reported. Clean Water Portland responded immediately by saying it was organizing an effort to have the issue put on the ballot. The group will need close to 20,000 signatures on petitions. The group says it has 125 volunteers lined up to gather signatures and anticipates having at least two dozen paid signature gatherers by the end of the week. The council vote followed a hours-long public meeting last week in which the pro- and anti-fluoride sides laid out their arguments, The Oregonian said. "This is the right thing to do, and I'm pleased to vote aye," Commissioner Dan Saltzman said prior to the vote. Commissioner Amanda Fritz said fluoride won't end cavities and more public education is needed but also voted in favor of fluoride. Commissioners Randy Leonard and Nick Fish also voted "aye," and Mayor Sam Adams made it unanimous.